Document updated by the store keeper that tracks the inventory kept of a single product in a particular bin.
Amount of stock equivalent to the consumption during the standard replenishment period.
Particular items in the inventory which are that committed to a particular order or transfer in the near future.
|Demand Signal||Any form of request to remove stock from a warehouse or storage facility coming in any format.|
Refers to any Any stored material, including both raw materials and finished goods. Also commonly referred as stock, though in the manufacturing sector, “stock” only comprises the finished products that are kept in the store.
Accountancy Accounting document or computer record that tracks inventory transactions (receptions and dispatches) in terms of quantity and value.
|Lead Time||The time lapse between the moment when the order is placed and the moment of its reception.|
The minimum quantity always available in stock to avoid shortage. It This is established important for products which that are critical or difficult to re-supply, and their shortage where shortages can jeopardize the a project plan. Minimum Stock = Buffer Stock + Safety Stock.
|On Hand Inventory|
Items in the stock that are available to be released.
Situation in which too much inventory is kept in the store.
The process of physically counting and verifying the goods in stock in order to reconcile data in records and on record with reality.
Period of time between two successive regular orders for a particular item in stock.
Level of extra stock that is kept to mitigate risk of Stockstock-out caused by uncertainties in supply and demand.
Document updated by the store keeper that tracks the inventory kept of a single product in the storage facility.
|Stock Keeping Unit (SKU)|
A unique code or nomenclature that designates a single line item of a larger consignment. SKUs may be tied to a specific production run or expiration date, and may denote only a product of specific characteristics.
Situation in which the inventory can’t levels cannot cope with the demand for a certain item .
|Time bucketThe time frame used to measure consumption and demand: days, weeks, months, quarters or years are the most commonly used|
and stock is fully depleted.
|Vendor Managed Inventory (VMI)|
Inventory management strategy in which suppliers take care of the manage physical inventory as part of their retailer’s inventory.
Inventory (or stock) management refers to the knowledge and the practices to keep of keeping the optimal amount of any amount of material in the a given storage facility. When holding maintaining a storage facility, inventory management becomes an integral part of the supply chain management. It is complementary to warehouse facility management and to the physical management of stored material.
Correct inventory management contributes to helps ensure the timely delivery of supplies. It Proper inventory management requires deep knowledge on of both , the acquisition process and the consumption patterns, and it is achieved broadly through three key activities:
In addition, the lack of inventory management can lead to increased holding costs, wasted stock or holding too much stock with the respective cost burden and risk increasedincrease.
Supply Chain Strategies
Inventory management is essential when relief supplies are transiting through a storage facility. There are several reasons why inventory management is key in the supply chain. The primary reason is to help deliver supplies in a timely manner. Managing the stock contributes to coping with the uncertainty acting as a buffer between demand and supply. This includes adjusting for lead times in the supply chain, which is particularly pertinent in the international procurement. In addition, a conveniently well managed inventory can contribute to economies of scale: buying large quantities can reduce the cost per item, though the ongoing storage costs must also be considered.
When keeping an inventory of for relief operations, it is highly recommended developing to develop a “stock policy” aligned with the organisational supply chain strategy. The stock policy should guide the organization Stock policies guide organisations on the decision process of keeping any type of stock in any location. Applying certain logic to the stock management is a the first concern for critical items in the relief operations and applicable to all type types of storage facility without regards to location or scalefacilities.
Stock policy is broadly defined by the following questions:
- Where should the inventory be located?
- What specific products should be available at each location? In , and in which quantities?
- When should inventory at a particular location be replenished?
- How much should be ordered to replace it?
The answers to these questions are dependent on two interrelated issues: the supply chain strategy and the type of stock holding.
For the purpose of this guide, “supply "supply chain strategy” strategy" refers to the logic behind the decision of moving goods through the supply chain. There are two main applicable strategies:
In a "push strategy," the need is anticipated before a real demand exists and the supplies are “pushed” into the supply chain. The most typical examples of “push strategy” in relief operations are common in: contingency supplies as part of an emergency preparedness plan, the opening of a new program, or in the supply of seasonal items like winter kits or mosquito nets (respectively stored before winter or before the malaria season starts).
Typically push systems operate when the demand is unknown in quantity or time. Quantities are usually based on estimations and driven by assumption on the situation that can generate the demand.
In a "pull strategy," the need is formally expressed by a consumer and the supplies are “pulled” into the supply chain driven by this demand. In relief operations the “pull strategy” is typically used during short term projects, construction or rehabilitation works or when supplying expensive equipment such as vehicles or telecoms material.
The pull system operates when the demand is known in time and quantity as a project whose outputs are predefined. Quantities are - quantities are clearly defined and the regular supply chain activities trigger demand signals based on quantities informed in the trigged from the final end of itthe supply chain. Generally, the pull supply chain strategy allows agencies to manage small or individual units of inventory accurately.
Type of Stock Holding
The initial logic of the of a stock holding will also determine the inventory management system in place. The most common types of stock holding in relief operations are:
Stock Buffer stock is stock that acts as a buffer between supply and demand. An inventory is kept because the impossibility to align them perfectlyIt is impossible to plan perfect quantities, and buffer stocks help even out unanticipated demand. Most of the decisions in buffer stock are taken based on how much of these items should be kept in the organisation's warehouse.
Stock is kept to consolidate Consolidated supplies of different in nature for further assembling is known as kitting or assembling. The In kitting, supplies are dependent on each other for delivery. Unbalances Imbalances of stock levels may lead to inefficiency , though as parallel inbound streams must be coordinated within the inventory. In addition, two different stocks should need to be managed: one for the original supplies and one for the assembled kits.
Stock is kept to split Splitting is when stock is split from large consignments in smaller lots to be delivered to different locations or consumers, sometimes at different moments. Mostly Splitting is mostly used to gain procurement efficiency and economies of scale. Attention must be placed Planners only need to manage a single inbound stream, but attending respond to demand signals from multiple consumers often with uneven demands. Consolidating these demands to calculate the amount to be ordered can result challenging. Larger be challenging, and larger buffer stocks may be required.
Stock Contingency stock is kept as part of a contingency plan. There is little inventory management as the contingency stock suffers minimal rotation. Nevertheless, if perishables are part of the contingency stock, they may be included in a rotational stock system.
Sock Vendor Managed Inventory (VMI) or virtual stock is kept in the vendor facilities until a release order is activated. The vendor keeps under reserve a specific number reserves specific amount of supplies as part of its own inventory or grants certain manufacturing capacity with a convenient specified delivery time. This is known as Vendor Managed Inventory (VMI) or virtual stock. Although this type of stock can be used for many purposes, it is commonly used as part of certain contingency plans.
In addition to the supply chain strategy and the type of stock holding, some extra considerations can be taken when defining a stock policy:
Financial Origin of The Product
The products in stock may have several financial origins:
- Procurement using donor funding.
- Procurement using own organisational internal funds.
- In Kind Donation -kind donation from an International Organisationorganisation, private sector, or NGO.
- Remaining materials from a particular project transferred to one or several on-going projects.
Depending on its origin, some management restrictions could be applicable: if products in stock are acquired with specific funding or for a specific purpose, the inventory levels must be managed accordingly. In some cases, these items can be considered committed inventory.
Nature of the Stored Goods
The type in and nature of stock can also influence how inventory is managed. Particular considerations should be taken with perishables, consumables (i.e., stationary) or products which that are essential to the program implementation , such as drugs in a health program, food in a nutritional program, or fuel.
Dependency Between Stock Items
Storing products with dependent demand means that products in the stock are directly related to other stock items, including:
- Kitting - the The consumption of one stock item means entails the consumption of both.
- Support equipment Equipment - spare Spare parts for a generatormachinery; the use of the generator implies requires the use of its replacement parts.
The demand for both products can either move in tandem (i.e., products belonging to a Non-food items kit) or in the opposite direction. Demand for a given product can be estimated based on the consumption of another supply.
Stock can be also categorised according to its financial value and the , while stock management can be influenced by the level of cost. This relative sock values. Understanding stock value can help to manage risks, to plan expenditure expenditures on new and replacement stock stocks, or to prioritise resources on the areas of greatest value. However, low-cost items can be crucial to some relief operations and should not be neglected.
In the field of inventory management, a Stock Keeping Unit (SKU) refers to a specific product type stored in a specific location. The term SKU also refers also to the a code made of letters and numbers , which that identifies a product in the store. An A SKU is not unique to each item (like bar-codes are), but the number used to identify each product type in the store. It designates a single item of a larger consignment. SKUs may be tied to a specific production run or expiration date , and may denote only a product of specific characteristics.
The SKU is intended as to be the most dis-aggregated level when of dealing with inventory, consequently, an . An inventory with multiple SKUs will require very different handling procedures than an inventory with few SKUs.
For example, when storing buckets , a decision must be taken regarding the pertinent characteristics that will define it as a SKU. Is it appropriate to consider account for all buckets as a similar article and considering them under the same SKU? Or is it pertinent to differentiate buckets by specific characteristics like: colour, size and material, thus creating three different SKUs? The correct SKU design will depend on the type of program and the product's intended use: if . If buckets are only used as part of an NFI kit to be distributed to the population, the colour of the bucket may not be important; But if . If buckets are used to segregate waste in health care facilities using colour coding, the colour of the bucket may be determinant to design SKUsvery important. Possible attributes for designation of a SKU:
- Dimensions (size)Dimensions
- Technical information
- Anything else
It must be considered that While SKUs are designed to keep track of inventory and to know how many the level of a specific product is available. They , they can also help to reconcile stock levels, to analyze analyse which products are more demanded, or to identify reorder point for products.
Managing Inventory Levels
Inventory management consists in keeping the optimal Keeping inventory levels optimal at all times . This is achieved when demand is furnished fulfilled on time while resources such as time, space, effort, and expenditures are efficiently managed. Deciding what is the appropriate inventory level , requires a good knowledge of demand patterns (forecast) and supply capacity (scheduling) - both are necessary to decide when to order and the period to be covered.
Movements of goods within a storage facility can be summarised in “INs” (when goods are received) and “OUTs” (when goods are delivered). The balance between inbound and outbound movements in the warehouse determines the inventory level. The quantity of stock delivered during a certain period of time is defined as consumption. It is , normally measured in items/time. The period of time between two successive regular orders for a particular item in stock is called "re-ordering cycle."
But goods Goods are not automatically restored in the warehouse - a re- an ordering process must take place. This means agencies Agencies must place an order of a certain quantity and waiting wait for its reception. The time lapse between the moment when the order is placed and the moment of its reception is known as “lead time”. The amount of stock consumed during a standard lead time is known as “buffer stock”.
Despite keeping a buffer stock, "stock-outs" may occur. Stock-outs are defined as stock of one or more items being fully depleted, and happen when the order is placed . Stock-outs occur when anticipated orders are long-overdue, the when actual lead times are longer than expected lead time is significantly exceeded times, or when consumption is significantly increased. To prevent this happeningstock-outs from occurring, a safety stock should be maintained. “Safety Stock” is the a quantity of extra stock that is kept to mitigate risk of stock-outs caused by uncertainties in supply and demand. Access constraints due to insecurity or Common examples uncertainties in relief operations might include access constraints, harsh climate events, or increased needs due to amplified vulnerability or to increased population in need, are common examples of context uncertainties in relief operations. Awareness on the humanitarian situation and the changing social conditions. Awareness changing situations and the associated potential supply chain bottlenecks can help designing planners design a safety stock appropriate to the operational context.
Once buffer stock and safety stock levels are defined, a “reorder level” should be established. Reorder level (or Re-Order Point - ROP) is the minimum stock level of any given item before another order is placed. It Reorder levels must be sufficiently larger high to allow regular replenishment of the stock before reaching a critical situation and a potential stock out. The reorder level is calculated by adding the safety stock to the buffer stock.
When defining reorder levels, agencies should consider that storage facilities have a limited capacity. Planners should define the maximum space available for each of the stored items and subsequently establishing establish a maximum stock level for each of ititem. This is especially critical when storing items requiring specific storage conditions, such as temperature sensitive goods or dangerous materials, for which allocating extra space may not be immediateimmediately available. To allow a certain degree of manoeuvrability, the “maximum stock” level should not be reached.
A correct Correct inventory management requires a broader vision than just inbound and outbound movements. Understanding different ways to visual visually manage inventory is especially important in certain supply chains with long transport stretchesperiods, limited storage capacity, or high rotation of items or where different orders overlap in time.
From the moment an item is ordered until the moment the item is received and then dispatched, the item can pass passes through different states:
- On hand/Running inventory is the Inventory - The current stock in the storage facility. It is the number of available units of a certain SKU for running operations.
- In transit inventory is the Inventory - The stock being transported between two locations. Although not in a warehouse, these supplies in transit remain as a property of the organisation and should be recorded/accounted. It is common that the sender deducts for senders to deduct an item from its inventory controls before the receiver accepts it. This In transit tracking is particularly important when transit between facilities or to a delivery location may take long periods.
- Committed inventory is the stock which - Stock that is committed to a particular order or transfer. While “On Hand” “on hand” inventory is the number of available units, “committed” inventory are items which are physically in the warehouse but are not technically available.
- Ordered inventory is the stock Inventory - Stock that has been ordered to replenish the inventory but that was is not yet received. If an order is partially received, the remaining quantity (pending to be received) is called back-order.In case that there is not enough inventory to cope with a request (because of receiving orders that are larger than on-hand inventory stock or because it is the first time an item is requested and the acquisition has not been yet completed), it is referred as inventory back-order. If inventory back-orders are a frequent occurrence, it may If inventory back-orders are a frequent occurrence, it may be necessary to evaluate the inventory control procedures.
"Demand forecasting" aims at predicting the is the process of attempting to predict future demand as accurately as possible using available data. Demand forecasting can be a simple task, but it can become far becomes more complex when managing inventories of many different products and/or when multiple customers with differing demand cycles that place orders concurrently.
A good forecast can be achieved by reviewing historic historical orders and consumption patterns. Consumption data is normally arranged in discrete time slots. Different time slots can be used depending on the frequency of outbound movements from the inventory: years, quarters, months, weeks, days. Though the time period granularity has to be defined according the context, the “monthly consumption” is the most commonly used. A monthly consumption is is the quantity of a particular item leaving the warehouse per month.
Recording and monitoring the consumption figures is the key activity to forecast. The simplest way to calculate the monthly consumption is by counting the deliveries recorded in the stock cardon stock cards or other tracking systems. The more records are available on historic historical consumption, the more accurate and reliable the forecast will be. Between three and ten previous “time slot” previous records periods can provide reasonable results for demand forecasting.
The demand Demand (D) can be established based on the average consumption of previous records. The average Average consumption is calculated by adding a number of consumption (C1– CN) figures and dividing by the number (N) of figures used:
Consumption can be calculated by reviewing historical periods of time in relation to key destinations or areas of intervention. In relief operations, consumption during the kick-off of an activity may be higher than in subsequent orders. This is commonly due to:
Stock managers should not consider forecast figures as a certainty. For critical items it is recommended to define alternative scenarios which reflect different possible future developments. The typical exercise to deal with uncertainty consists in of designing a best and a worst-case scenario in addition to an average case forecast.
To define demand in worst and best-case scenarios, planners should identify the maximum positive (and negative) variation (Vmax) over the last recorded time periodsperiod, and add (or deduct) the Vmax to of the average monthly consumption.
Depending on the context and the type of inventory, seasonal fluctuations may appear. Data based on previous years or consumption figures, or of previous interventions can help to prevent stock-outs or over-stocks due to seasonal seasonally increased or decreased demand. It is recommended to check previous annual demand signals to identify and understand seasonal patterns.
Using annual data to calculate average monthly consumption can help to balance sporadic high demands: surplus stock built up during low consumption periods should compensate higher demand during high consumption periods. If agencies plan to hold unused stock for anticipated higher demand, they must ensure that stock will not expire or become unusable by the higher period of anticipated demand. Pre-positioned or new stock items may not be a major issue, but inventory delivered to a country may already be approaching the end of it's life its life and must be used accordingly.
If seasonal fluctuations are substantial and average consumption between different months differ significantly, seasonal stocks with specific thresholds could be considered. In such cases demand forecasts must accommodate the time-frame and the period in the year to be covered.
Limitations of Forecasting
While forecasts can be useful for smoothing out demand curves and predicting seasonal needs, they also come with their own limitations, especially in the humanitarian context. An inappropriate demand forecast can lead to stock wastage in the form of unused items piling up, or major stock outs.
A demand forecast should never be confused with the goals of a project. Humanitarian projects often run on expected population numbers or goals reported to donors. A demand forecast should be built upon real consumption data and informed by demand signals, not the desired distribution numbers. Early in a humanitarian intervention, it can be hard or impossible to know what real consumption numbers will be, and project plans or available funds are is the only thing data to work from. After a project has been running for a few months however, any given forecast must be revisited.
Based on demand data, a replenishment plan for the inventory must be designed. This A replenishment plan consists in of deciding when to order and the quantities to order in the period to be covered.
The decision on of when stock should be replenished and when an order should be placed is crucial for successful inventory management. Two different methods can be applied:
A third method includes reacting to dynamics external to the storage facility, such as budgetary cycles or combining orders together with other agencies as part of a network or consortia. If the inventory management is runs the risk of being exposed to such external dynamics, coordination with relevant stakeholders is key for anticipation.
Agencies should decide if a single method should be applied, or if switching from one method to the other is more useful. This decision depends on criteria such as:
- The phase in the relief intervention: is it Is the supply chain responding to a stable long-term program? Or the opening is it responding to the early phases of a response to a sudden onset emergency with high levels of uncertainty?
- The standard delivery time of the orders: Are the supplies sourced from the local market taking short time lead times to get the ordered items? Or the supplies are sourced in international market with long lead times?
- The supply chain strategy: is the supply chain operating under a push or pull strategy?
- The number of different products ordered simultaneously: Although forecasting may be done on the level of SKU, it is a common practice to order on the level of a product group or supplier. The products Product grouping can be designed according to the market and supplier (i.e., construction materials, drugs, hygiene) or according to demand dependency (i.e., kits).
Systematic orders based on a pre-established frequency is a common practice in:
Systematic ordering is the most efficient method is to refill inventory as it establishes working patterns and distributes the workload regularly throughout time. However, it Systematic ordering also requires good planning, team discipline and reasonable forecasts.
The re-ordering cycle is directly related to the demand (D) and the quantity to be ordered (Q): the larger is the quantity ordered, the longer will be the period between orders. The higher is the demand (D), the shorter will be re-ordering cycle.
In general, a 5% to 10% buffer can be kept as a margin from the maximum stock level to avoid over-stocks after periods of lower consumption. In cases where the re-ordering cycle is constrained because of limited storage capacity, consider alternative storage facilities to decrease the stress in the supply chain.
There are several mathematical models in commercial logistics to calculate the optimal re-ordering cycle. One of it these models is based in on the demand and the economic variables only (costs of reordering an item and the cost of holding it in the inventory). It is referred as the Economic Order Quantity (EOQ) model:
Nevertheless, estimating the costs of reordering and holding an item in the inventory can lead to complex calculation processes and is only recommended for well-established and mature supply chains.
Consider that misalignment between expected inventory levels and real inventory levels for certain items may happen due to fluctuations on demand, or variations in lead time. Corrections to the pre-established frequency of orders can be done after certain re-ordering cycles have been completed. Nevertheless, it is recommended to stick to clear and easy-to-remember frequencies: monthly orders, quarterly orders, bi-annual orders or annual orders. This will ease the coordination between the different stakeholders all along the supply chain.
A second method to decide when to place an order for stock replenishment, consists of monitoring stock levels and placing orders whenever they reach the pre-established re-order level. This method is normally applied under pull supply chain strategies, or at the beginning of new programs when consumption records are unavailable, or when the concerned articles are easily accessible with short lead times.
Special attention must be taken when storing articles with dependent demand or when requiring kitting for order processing. Stock items with dependencies on lower stock levels will determine the need to launch an order for a whole group of items, if required.
Refer to point Systematic Orders under pre-established frequency in this chapter to understand how to calculate the re-order stock level.
Calculating Order Quantities
Demand (D), re-ordering cycle (Ro) and the quantity to be ordered (Q) are closely related. The longer is the period between orders, the larger the quantity to be ordered. If demand increases, the larger the order placed.
<center><table> <tr><td><font size="6"> Optimal Re-Ordering Cycle = </font> </td> <td> <table> <tr><td> <font size="18"> √</font><font size="14">(( </font> </td> <td> <table> <tr> <td> <center><font size="6"> 2 </font></td> </tr> <tr><td bgcolor=000000> </td></tr> <tr><td> <center><font size="6"> D </font></center> </td></tr> </table> </td> <td> <font size="14"> ) x ( </font> </td> <td> <table> <tr> <td> <center><font size="6"> C</font><font size="4">R </font></td> </tr> <tr><td bgcolor=000000> </td></tr> <tr><td> <center><font size="6"> C</font><font size="4">H </font></center> </td></tr> </table> </td> <td> <font size="14"> )) </font> </td> </tr> </table> </td></tr> </table> </center>
Nevertheless, estimating the costs of reordering and holding an item in inventory can lead to complex calculation processes and is only recommended for well-established and mature supply chains.
Misalignment between expected inventory levels and real inventory levels for certain items may happen due to fluctuations in demand or variations in lead time. Corrections to the pre-established frequency of orders can be done after certain re-ordering cycles have been completed. It is recommended to stick to clear and easy-to-remember frequencies: monthly orders, quarterly orders, bi-annual orders or annual orders. This will ease the coordination between the different stakeholders all along the supply chain.
Pre-established Thresholds/Minimum Re-order Levels
A second method used to decide when to place an order for stock replenishment, consists of monitoring stock levels and placing orders whenever they reach the pre-established re-order level. This method is normally applied under pull supply chain strategies, at the beginning of new programs when consumption records are unavailable, or when the concerned articles are easily accessible with short lead times.
Special attention must be taken when storing articles with dependent demand or when requiring kitting for order processing. Stock items with dependencies on items with lower stock levels will determine the need to launch an order for a whole group of items.
Refer to the section Systematic Orders under pre-established frequency in this chapter to understand how to calculate the re-order stock level.
Calculating Order Quantities
Demand (D), the re-ordering cycle (Ro) and the quantity to be ordered (Q) are closely related. The longer the period between orders, the larger the quantity to be ordered. If demand increases, the larger the order that will need to be placed.
Independently of the re-order level, the quantity to be ordered (Q) can be calculated at any given time based to the following variables:
- Demand (D),
- Lead time (LT)
- Time period to be covered by the order (T)
- Stock level (S): the running stock at the given time
- Items in the pipeline (P): ordered inventory, transit inventory, back orders, loan reimbursements, etc.
The basic calculation for the quantity to be ordered (Q) considers the demand during the period to be covered (T x D), plus the demand during the lead time (LT x D), subtracting the quantities in stock (S) and the quantities in the pipeline (P):
<center><table> <tr><td><font size="10"> <i>Q</i> = </td> <td> <td> <center><font size="10"> <i>T.D</i> + L</font><font size="6">T</font><font size="10">.<i>D - S - P</i> </font></center> </td></tr> </table> </center>
If preparing an order when inventory reaches the pre-established re-order level, the quantity to be ordered (Q) will be calculated in the same way but using the re-order level instead of the running stock level.
<center><table> <tr><td><font size="10"> <i>Q</i> = </td> <td> <td> <center><font size="10">
Independently of the re-order level, the quantity to be ordered (Q) can be calculated at any given time based to the following variables:
- Demand (D),
- Lead time (LT)
- Time period to be covered by the order (T)
- Stock level (S): the running stock at the given time
- Items in the pipeline (P): ordered inventory, transit inventory, back orders, loan reimbursements, etc.
+ L</font><font size="6">T</font><font size="10">.<i>D - Ro - P</i> </font></center> </td></tr> </table> </center>
In cases where the safety stock (SS) must be replenished (totally or partially) the required amount should be added to the previous formula.
<center><table> <tr><td><font size="10"> <i>Q</i> = </td> <td> <td> <center><font size="10"> <i>T.D<<i>S</font><font size="6">S</font><font size="10"> + T.D </i> + L</font><font size="6">T</font><font size="10">.<i>D - S - P</i> </font></center> </td></tr> </table> </center>
If preparing an order to be launched when inventory reaches the pre-established re-order level, the quantity to be ordered (Q) will be calculated in the same way but using the re-order level instead of the running stock level.
<center><table> <tr><td><font size="10"> <i>Q</i> = </td> <td> <td> <center><font size="10"> <i>T.D</i> + L</font><font size="6">T</font><font size="10">.<i>D - Ro - P</i> </font></center> </td></tr> </table> </center>
In cases where the safety stock (SS) must be replenished (totally or partially) the required amount will have to be added to the previous formula.More sophisticated models can be applied to calculate the optimal quantity of goods to order. The Economic Order Quantity (EOQ) model can be used for computing the economic optimal quantity of goods while ordering. This model is based in economic variables such as the ordering costs and the holding costs. It defines the optimal quantity as a balance between increased costs due to holding a lot of stock, and the economy of scale obtained when making big orders.
According to the EOQ model, the optimal quantity to be ordered is defined by the annual demand quantity (D), the costs per order (CR) and the holding costs (CH), as follows:
<center><table> <tr><td><font size="106"> <i>Q</i>Optimal Economic Ordering Quantity = </font> </td> <td> <td><table> <tr><td> <center><font<font size="1018"> <i>S<√</font><font size="6">S</font><font size="10"> + T.D </i> + L</font><font14">( </font> </td> <td> <table> <tr> <td> <center><font size="6">T<> 2.D.C</font><font size="10">.<i>D - S - P</i>4">R </font></center>td> </tr> <tr><td bgcolor=000000> </td></tr> </table> </center>
More sophisticated models can be applied to calculate the optimal quantity of goods to order. The Economic Order Quantity (EOQ) model can be used for computing the economic optimal quantity of goods to order. This model is based in economic variables such as the ordering costs and the holding costs, and it conceives the optimal quantity as a balance between increased costs due to holding a lot of stock, versus the economy of scale obtained when making big orders.
According to the EOQ model, the optimal quantity to be ordered is defined by the annual demand quantity (D), the costs per order (CR) and the holding costs (CH), as follows:
<tr><td> <center><font size="6"> C</font><font size="4">H </font></center> </td></tr> </table> </td> <td> <font size="14"> ) </font> </td> </tr> </table> </td></tr> </table> </center>
The basic purpose of the inventory control is to know at any given moment what supplies are in a given storage location or warehouse. Inventory control is a cornerstone of good inventory management.
Moreover, inventory Inventory control ensures traceability and transparency of any storage activity, providing accurate information on any movement of supplies including:
- Where the products come from.
- When the products were received and in which quantities.
- Where the products have gone.
- When the products were dispatched and in which quantities.
Inventory control improves stock management practices and to support supports decision takingmaking through:
- Optimising working processes and costs.
- Providing some degree of protection against potential over-stocks or stock-outs.
- Anticipating products getting expired or close to expire.
- Detecting loses or any deterioration of the stored products.
In addition, inventory Inventory control is essential for accountability, providing for instance, the value of the items kept in the store and reporting about the items unconsumed from a project values of stored items and consumption status from projects close to conclusion. In summary, Proper inventory control will provide value to the storage facility facilities through optimised management and , higher levels of satisfaction among customers and stakeholders as products and information can be available on demand.
For a successful inventory control three critical activities must be accomplished:
- Systematic recording and keeping support documentation accessible.
- Monitoring consumption, stock levels and inventory performance.
- Reporting to feed decision making.
Systematic Recording and Support Documentation
There are two main types of records that enable proper inventory control: those controlling tracking stock movements and those controlling tracking stock levels. Both types are related to each other connected as each stock movement affects the level of stock . Therefore, they in any given location. Records should be formally cross-referenced allowing traceability of each item from reception to dispatch.
The documenting system in place should be as standard as possible but while still avoiding unnecessary complications. The The system needs to be established at the onset of operations and fully understood by the staff whose job it is to put it into practice. The training Training of the warehouse personnel is crucial in this sense.Controlling stock levels
Recording Stock Levels
The basic purpose of the inventory control is to know , at any given moment , what supplies are in the warehousea storage facility. There are different levels of granularity in terms of recording stock levels.
Where stocks are held for different donors, it is may be convenient to keep separated records for each donor. This will ease accountability and reporting processes, especially at the closure of the project.Records of stock movement
Recording Stock Movement
All movements (in and out) of stock should be duly recorded and backed supported by the corresponding documents certifying receipt or dispatch of supplies. In addition, all supplies Supplies should change hands only when the corresponding document has documents have been signed by the next recipient link in the supply chain. All these documents involved in the exchange of goods must be duly archived.
All goods received in the storage facility should be accompanied with a Waybill waybill or a Delivery delivery note note describing the supplies details and its the item origin. If the a supplier or transporter does not provide the a waybill or a delivery note, the storekeeper should fill in a goods received note. A copy of the signed document should be retained by both the recipient and person delivering the goods.
To dispatch a product from storage, a Stock Release Order duly authorised fully authorised stock release order should be provided. Without the stock release order, the storekeeper should not release any product. A delivery note should be prepared, duly signed by both parties (deliverer, receiver/transporter) and archived.
All transaction documents should clearly specify the name and exact quantity of the supplies received/released, as well as names of the individuals or agencies issuing and receiving them. The reference number of the transaction should be included on the related stock cards, allowing full traceability of any goods in the stock.
It is key that all stock receipts, issues, transfers, disposals and adjustments are documented and authorised. Do not postpone any of the essential recording tasks; all stock movement records must be updated immediately. Hard copies of stock cards and waybill/delivery notes should be kept properly archived within the warehouse premises, and be accessible to authorised persons.
Consistent records will enable proper monitoring. Basic things to be regularly monitored are:
- Stock levels, with an especial regard toLevels of stock with special requirements:
- Items reaching critical thresholds (like re-order or safety stock levels).
- Items belonging to specific projects reaching to its end.
- Items close to expirewith expiry dates.
- Consumption patterns, and the length of time that inventory will last if under current usage continues. With with special attention to:
- Items with high rotation.
- Items which that are core to running relief operations.
- Items with short order cycles.
- Items with a significantly increased demand that could lead to stock-out situations.
- Items with a significantly reduced demand that could lead to over-stock situations.
In addition, the performance of inventory management can also be monitored. To adjust the management processes, consider monitoring the following information:
- Inventory turns - transactions (in and out) rotations - Transactional frequency, volume and value, identifying those items with higher turn-over. The value of the individual transactions can be compared to the average inventory value and to the required workload for its completionto manage them.
- Time Actual time to completion - Time from issue of The amount of time from issuing instruction to completion of a task (i.e., Time . This might include the time for dispatch preparation, considering including the time lapse between the moment when the stock release order is received and when goods formally dispatched).
- Number of stock-outs in a given period.
- Stock valuation.
- Quantities and values lost.
When coming to control and monitor particular items, consider that stocks follow the Pareto principle, also known as the “80/20 rule”, the “law of the vital few”, or the “principle of factor sparsity”. This principle states that roughly 80% of consequences come from 20% of the causes (the “vital few”), which . When applied to inventory management is translated to: , 80% of the movements are tend to come from 20% of the list line of items. Identifying this 20% of “high-turn” rotation” items is vital for an optimal inventory management.
Regular control can be achieved dividing the inventory in A, B and C groups and counting a rational combination of each category per dayper period of review. This type of counting where occurs when some parts of the stock on hand are counted more often than others, usually following a schedule, is referred as “Cycle Counting”.
- General physical inventory: Typically happens in predefined periods such as on a yearly, semester or quarterly basis and covers the whole inventory in a given storage facility.
- On demand inventory of specific items: For some specific reports or requests, particular particularly for items that may have require more regular counting.
- Inventory by sample: Random spot checks usually performed by request of audit auditors or program management. Random spot checks are good to carry out during random or infrequent visits.
Physical inventory require stock to remain stationary, meaning that When conducting physical inventories, stock should remain stationary - no stock movement should be performed for those items under scrutiny. On demand or random spot checks are easier to conduct and may occur as needed; during random spot checks or on demand inspections only movement of the selected stock item should be halted. A full physical stock count will require the entire facility to be closed to stock movement for a pre-defined period of time.
Random Spot Checks
Random spot checks are encouraged throughout any operation, and at any time. They are useful for when counters only have access to storage facilities for limited periods of time, due to security or operational constraints. Spot checks are also a relatively low effort way to continually monitor activities as well.
To conduct a spot check, counters should pick out 3-7 line items from any random consignments from cargo item in the warehouse ledger and conduct a blind count. To facilitate a blind count, locate the items in the warehouse.
- If the items cannot be located, ask the storekeeper or warehouse manager to help locate them.
- The inspector should conduct their own count, and ask the warehouse officer third-party or other team member to do a separate count conducted at the same time.
- And At the end of both counts, compare the two numbers should be and reconcile any discrepancies between the two counts.
- Cross-check between the physical count and the stock count in the warehouse ledger afterwards. If the physical count does not match the numbers on the ledger, counters should make a note of the discrepancy.
- Weigh and measure the 3-7 selected items.
- Cross check against the weights and volumes in the warehouse ledger. Discrepancies in weights and dimensions so should be recorded and fixed.
Full General Physical Inventory
When general physical inventory happens, the warehouse should be locked down during the whole entire inventory period. The overall size of the warehouse and quantity of items stored within it will determine the length of time required to complete a full count. A small facility could be completed in a just a few hours, while a large facility might take several days.
In order to mitigate the chance of human mistakes error and bias, it is recommended that two separate teams count the same set of items without any information exchange between them. A third person should be appointed to oversee or manage the counting teams. If available, employ the “stock tag” system to facilitate counting.
|Inventory Sheet||Stock Tags|
While on-demand or random spot checking may occur as needed, it is strongly advised that a full stock count should be conducted at least once a year, if not more frequently depending on the size of the facility and the overall volume of throughput. The standard accepted best practice for a full stuck count is called “double-blind”, and follows the below steps:
|Double Blind Counting Procedures|
Once a physical inventory is complete, the counter should record discrepancies for further analysis and follow up.
- Loss – There are fewer of one or more line item than is recorded in the warehouse ledger, and there are no waybills/release files to substantiate explain the difference.
- Expired/Spoiled/Infested – Items are considered unusable because they are past their expiration date or infested.
- Surplus – There are more than one or more line item items than is are recorded in the warehouse ledger, and there are no waybills/received notes to substantiate explain the difference.
- Damage – Stored items are found to be too damaged to be usable by the service requester.
- Mislabelled – Stored items have been erroneously listed as a different item or belonging to a different consignment project in the warehouse ledger.
- Unidentified – Stored items do not appear to be associated with any known other item or consignment project in the warehouse ledger.
- Incorrect Dimensions – Stored items have incorrect volumetric or weight measurements than what is recorded in the warehouse ledger, or no measurements are recorded at all where required.
- A warehouse worker or a loader may confuse two similar line items from two consignments projects and store them together as one.
- Cargo is released by the owner, but the warehouse manager forgets to update the warehouse ledger.
- Cargo was recently received but not yet recorded on the warehouse ledger.
Only a full physical inventory will tally the total numbers of all items on hand. If counters find loss or mislabelled cargo during random spot checks, additional investigation may be required to understand the full problem.
|In cases of loss, spoilage or damage:||Counters should reinspect items and conduct additional counts if required. If loss or damage still persists after additional counts, then a loss report must be filled out, and the warehouse ledger must be updated. The owner of the cargo must be informed of the loss.|
|In cases of mislabelled or unidentified cargo:||Counters and warehouse staff should correctly link cargo to consignments/ anticipated deliveries. Mislabelled cargo should be properly labelled, an updated stock card placed with the items and the warehouse ledger updated. Unidentified cargo should be linked to a consignmentproject, donor, budget code or category as required, and be properly labelled in the warehouse and updated in the warehouse ledger. If no information on the cargo exists, warehouse staff must investigate where the stored items may have come from.|
|In cases of surplus cargo:||Counters and warehouse staff should reconcile cargo movements with stock on hand. If there is no explanation for additional items discovered, warehouse staff must investigate where the stored items may have come from.|
|In cases of mis-measurement:||Newly corrected measurements – weights and volumes – should be updated in the warehouse ledger.|
The frequency and number of inaccuracies should be regularly monitored for each warehouse location. Any stock discrepancy should be reported and analysed and corrective actions should be taken to reduce the risk of further inaccuracies. The logistics team should record the results of general inventories in a file specific to that warehouse location. If a warehouse continues to perform below the acceptable standards, corrective action or training may be required.
Reporting mechanisms aim to consolidate and communicate all the monitored informationdata, especially those signs requiring further action.
- Regular reports.
- Ad-hoc reports.
Regular reports are should be produced in meaningful useful time intervals, normally: weekly, monthly, quarterly or yearly. They Reports contribute to general program management, to follow help with following up a specific inventory and to feed items, assist supply chain strategic decisions, improving inventory related working processes and updating and help update forecasting figures and critical stock thresholds.
The intervals for the reports can be set based on the turn-over of the articles and/or the location of the storage facility. As an example, the reports from the storage of a health facility storage running a nutritional program with weekly receptions daily patients and daily deliveries of ready-to-use therapeutic food, can be established medication might want to establish reports in weekly intervals.
Regular reports can include information such as:
- Stock Summary: A record of the relevant transactions and stock levels. For all or a particular list of relevant items : period during a pre-set time period, this might include opening and closing stock levellevels, average consumption during the period, and total receptions receipts and dispatches. The value of the transactions and the value of the balance quantity may be relevant for some inventories. Perishable products must be included in this summary.
- An outline of those items reaching a pre-established stock threshold and thus, requiring re-ordering or other action.
- An outline of those items approaching their date of expiry.
- Key performance indicators, based on the information mentioned in the Monitoring section on the performance of the inventory management.
Fig.: Weekly inventory monitoring report from an outreach stock, part of a Nutritional program with daily distribution of food items and non-food items
The regular Regular reports should be shared with relevant stakeholders, especially those making use of regularly stored items. It is a common practice to crosscheck the cross-check information in the inventory reports with the expected and current number of attended beneficiaries.
In addition to regular reports, the storekeeper storekeepers should inform the pertinent individuals when relevant inventory events occur:
- The stock level of an article reaches the re-order level.
- One or several stock items are losslost, damaged or spoiled. In such cases, a loss report should be completed.
- A stock discrepancy (positive or negative) is identified.
- A project is reaching to its end. This should be done according to donor regulations.
There should be considered the ability to produce management reports on stocks per project.
Reliable, up to date and accessible information is of key importance for inventory management. Data management will enable making the correct information available to the correct people in the required moment. Furthermore, data management is a cornerstone for accountability.
Procedures and means should be in place to ensure that records are properly kept for internal and external use. The basic Basic information to be recorded and kept updated is mentioned in the previous section the systematic recording and keeping support documentation section.
Formats: Physical or Electronic
The means to store and manage stock data can be physical (hard) or electronic (digital). According to the needs, both means methods can be combined and used to compliment complement each other. In case of using both systems simultaneously it is highly recommended to keep one as a“master a "master file”, and the other as back-up.
- Urgency to setup inventory operations: physical Physical data record formats can be set immediately, always accompanied by a basic training. Digital formats can take longer time-frames depending on the operational environment and the organisational culture and preparation on the matter.
- Existing funds: the The level of investment is considerably higher for the setup of electronic data management means.
- Digital literacy of staff: in In some particular contexts, the staff will be interested better able to adopt and use digital systems, while in other , some resistance may occur.
- Environmental conditions: access Access to reliable power supply and reliability of the internet connection.
In general, working with digital records should can improve data reliability and access to information, enhance make working processes making them more efficient, optimise the use of space avoiding the storage of big volume of archivesreduce space to store physical files, and increase the safety of the data and easing its recovery if needed. Also, digitising the records will reduce the use of paper and other stationary.
Digital records, similarly Similar to physical archivingfiling, must digital records should be kept under certain order and logic. Folders and files related to inventory management should follow an agreed standard in terms of name and location, enabling the search searching for a specific file or group of files. Furthermore, the people accessing the data and how they use it must also be convened and controlledPersons accessing digital files data should be trained in the process, and access granted to only relevant people.
Physical file data management is recommended in temporary setups, when such as opening new emergency operations operation or in locations with unreliable power supply or with limited access to information systems.
Physical records require proper format and labelling, ideally in a standardised manner. A suitable location, secure and but still accessible , location should be designated within the storage facility to keep hard files under use. Files files, while files from past periods should be kept aside in a secure place. The time period to be covered by the running folders for the active physical files should be defined in a coordinated manner with other relevant departments. It is a common practice to make use of natural years, though this may differ depending on the organisation and the type of data. For example, waybills or delivery notes may be archived as per natural years while stock cards may follow a different logic.
When using physical records, consider that carton or heavy paper is more expensive and less environmentally friendly, but more durable during intensive use. Files It is recommended to use carton or heavy paper for files requiring frequent access and update updating, such as stock cards are recommended in carton or heavy paper.
Using physical data management formats will still require frequent consolidation of stock records record information into a system / excel spreadsheet. A daily or weekly consolidation is advised rather than making it monthly. More frequent consolidation will improve data backup, will provide faster access to information in case of need, and will avoid additional burden in particular periods of the month.
Whatever is the format for inventory data management, physical or digital file formats are used, a coding system should be in place to ease information flow. Standardised codes and labels serve as a shorthand, or abbreviated item description. The use of codes should speed references to stored articles, files and entities of interest such as locations, providers, clients, donors, etc. In addition, a proper coding system should will enable data segregation, cross-referencing and ultimately, analysis.
- Geographic information: Region, Countrycountry, Districtdistrict, Officeoffice, etc.
- Supply chain entities: Suppliers and sources, Clients clients and destinations, Departmentsdepartments, warehouses, etc.
- Locations within the storage facility where items may be stored: roomsRooms, corridors, shelves, stacks, etc.
- Operational information: programProgram, project, donor, etc.
- Units of measure: “pcs”, “Kg”, “bags”, etc.
- Time scales: dateDate, year, week, etc.
|Carton LabelingLabelling/Coding||Shelf LabelingLabelling/Coding|
As preliminary step, a consistent, unique and well-organised set of descriptions per inventory function should be designed and agreed upon in advance, including: covered geography, relevant stakeholders, locations, type of stored items, etc. Critical elements to be identified through codes should be outlined. Avoid over-coding: not all the fields above mentioned are always relevant to be coded.
Labels and codes should be easy to read and , unambiguous, and harmonisation with other departments and other supply chain units within the organisation or key partners should be contemplated. An agency's finance department may be a key collaborator in this task.
The use of codes should be central to inventory management; , therefore it should be included in inventory management procedures. In addition, the staff Staff should be trained to know on how to follow themcodes, making the way inventory is handled and records are kept consistent across the operation.
Inventory management can be is central for timely implementation of humanitarian relief operations. For a successful and valuable stock keeping, inventory activities must be synchronised with other activities from stakeholders external to the storage facility: suppliers, transporters, clients, other departments, etcand others. Key information must be regularly gathered and delivered from and to relevant stakeholders.
Transit inventories should also be closely followed. This can be done by gathering information from suppliers or supply chain managers on the current status of local, national and international orders. This Tracking in transit inventory will allow planners to properly prepare a given storage facility for shipment reception or to alert clients on the imminent delivery of a pending request or a back-order.
Whenever possible, coordination should also help to anticipate intensive use of the inventory (i.e., such as during emergency responses , or distribution periods, etc.). In such situations, extra resources such as increased labour or extended working hours should can be made available.
Potential spikes or steady increases or reductions of demand should also be prevented through coordination. Operational information such as new activities, an increase in the number of people in need or access restrictions to deliver in a certain area, are critical in this sense and can help to prevent situations stock-outs or over ordering.
Coordination should especially be granted used during the beginning or ending of projects. Particular donor requirements related to stock keeping must be communicated, with especial special attention to specific reporting mechanisms and dealing with remaining stockdisposition regulations.