Inventory Management Guide

Inventory management is the process of tracking, controlling, and replenishing the goods a business buys, stores, and sells. Done well, it prevents stockouts and oversells, keeps carrying costs under control, and gives every part of your operation — purchasing, fulfillment, and finance — a single accurate picture of what you have.

For ecommerce sellers, inventory management gets complicated quickly. Sales arrive from multiple channels simultaneously. The same SKU may be stored across two warehouses and bundled into a kit sold on three different storefronts. A supplier ships late; a return comes back damaged; a flash sale clears 400 units in an afternoon. Manual systems — spreadsheets, platform-native stock counts — crack under these conditions. This guide explains how inventory management works, what the core methods are, and how to know when you've outgrown your current approach.

What Is Inventory Management?

Inventory management encompasses every activity involved in sourcing, tracking, and moving physical products through your business:

• Purchasing — deciding when to reorder, from which suppliers, at what quantities and costs
• Receiving — logging incoming stock against purchase orders and updating on-hand counts
• Storage — organizing inventory across warehouse locations so the right items are findable and accessible
• Tracking — maintaining accurate stock counts in real time as sales, receipts, adjustments, and transfers occur
• Fulfillment — allocating inventory to orders and shipping from the right location
• Replenishment — forecasting demand and triggering restocking before you run out

The goal of all of it is a single number: an accurate available-on-hand count per SKU, per location, at every moment.

Why Inventory Management Is Important

Poor inventory management has direct, measurable costs. The most common failures and what they cause:

Stockouts occur when you sell more than you have in stock. For ecommerce sellers, a stockout means cancelled orders, negative reviews, potential marketplace account flags (Amazon's fill rate requirements are strict), and lost revenue that doesn't come back — buyers find a competitor. The bigger the sales volume, the larger the per-day cost of a stockout.

Overselling is a multichannel-specific version of a stockout. If your Shopify store and your Amazon listing both show 10 units available, and two customers buy simultaneously, one of them gets cancelled. Platform-native inventory doesn't prevent this — each channel only sees its own count. Only a system that shares inventory across channels and commits stock immediately at order arrival prevents it reliably.

High carrying costs occur when you hold too much inventory for too long. Carrying cost — the cost of holding inventory — typically runs 20–30% of the inventory's value annually when you include storage, insurance, capital tied up, and risk of obsolescence. Excess inventory is not just idle; it's actively expensive.

Inaccurate counts cascade into every other system. Finance can't calculate cost of goods sold accurately. Purchasing can't tell when to reorder. Fulfillment can't tell if an order is actually shippable. A single trusted inventory count is the foundation every other function depends on.

Types of Inventory

Different types of inventory require different tracking approaches:

Raw materials — components purchased from suppliers to manufacture finished goods. Tracked by quantity on hand and committed to open manufacturing orders.

Work-in-progress (WIP) — goods partially assembled or in production. Important for manufacturers and businesses that build kits or bundles from components.

Finished goods — completed products ready to sell and ship. The primary focus for most ecommerce businesses.

Safety stock — buffer inventory held above your minimum reorder threshold to absorb demand variability and supplier lead time uncertainty. Too little and stockouts happen; too much and carrying costs rise.

MRO inventory — Maintenance, Repair, and Operations supplies (packaging, tape, printer supplies). Often untracked but can represent meaningful cost at scale.

The Inventory Management Process

Inventory moves through a predictable cycle. Understanding each stage helps identify where your operation is losing accuracy.

1. Demand forecasting and purchasing

Review sales velocity, seasonality, and lead times to determine what to order and when. Set reorder points per SKU — the quantity at which a new purchase order should be triggered. Create purchase orders against specific suppliers with quantities, unit costs, and expected delivery dates.

2. Receiving

When supplier shipments arrive, receive them against the open purchase order. Count and scan incoming items; log any discrepancies (shortages, damages, substitutions) on the PO. Only received quantities update on-hand counts — this creates a formal receiving record and prevents inventory from being inflated before goods actually arrive.

3. Storage and organization

Stock items in assigned bin locations. Good location logic (high-velocity items nearest the packing station; size-appropriate shelving; SKU labels readable from the aisle) reduces pick errors and pick time. For multi-warehouse operations, inventory is tracked per location independently.

4. Order fulfillment

When a sales order arrives, inventory commits to that order immediately — reducing available-on-hand so the same units can't be allocated twice. A pick list tells warehouse staff which items to retrieve, from which locations, in what quantities. Packing verification (scanning items before the label prints) catches mispicks before they ship.

5. Shipping and tracking pushback

After shipment, tracking numbers post back to the originating sales channel automatically. Fulfilled orders decrement physical on-hand inventory. Updated counts sync to all connected channels.

6. Replenishment

On-hand counts drop as orders ship. When a SKU's available quantity falls to its reorder point, a new purchase order is triggered — manually or automatically, depending on your setup. The cycle begins again.

Inventory Control Methods

Inventory control methods are the rules that govern how you value inventory and in what order you deplete it.

FIFO (First In, First Out)

The oldest stock is sold first. For most physical goods — especially perishables, apparel, and anything with a shelf life or model year — FIFO prevents holding old inventory past its useful life. It's the most common method for ecommerce businesses.

LIFO (Last In, First Out)

The newest stock is sold first. LIFO is used in some accounting contexts (it increases COGS during inflation, reducing taxable income) but is not permitted under IFRS and is rare for physical ecommerce businesses.

Weighted Average Cost (WAC)

Each receipt from a supplier is blended into an average cost per unit across all units in stock. When units sell, the cost of goods sold uses this average rather than specific lot costs. WAC smooths out cost volatility when supplier prices change between POs and is the standard method in inventory management software.

Specific Identification

Each individual unit is tracked by serial number or lot number, and cost is assigned precisely to that unit. Used for high-value items where individual unit tracking is worth the overhead (electronics, jewelry, vehicles).

ABC Analysis

Categorize your SKU catalog by contribution to revenue and velocity:

• A items: High-value, high-velocity SKUs — typically 10–20% of your catalog but 70–80% of revenue. These get tight reorder points, frequent cycle counts, and buffer stock.
• B items: Mid-tier — standard replenishment cadence, quarterly counts.
• C items: Low-value, slow-moving — wide reorder triggers, annual counts, candidates for discontinuation.

ABC analysis is the inventory application of the Pareto Principle (80/20 rule): roughly 80% of your revenue comes from 20% of your SKUs. The framework focuses operational attention where it has the biggest impact rather than treating all products equally.

Just-In-Time (JIT)

Order inventory to arrive as close as possible to when it's needed, minimizing the quantity held on hand at any given time. JIT reduces carrying costs and storage requirements but increases exposure to supply chain disruptions and lead time variability. It works best when supplier reliability is high and demand is predictable. See: JIT Inventory Management in CPG

Economic Order Quantity (EOQ)

A formula that calculates the optimal order quantity to minimize total ordering and holding costs:

> EOQ = √(2DS ÷ H)

>

> D = annual demand units · S = cost per order · H = annual holding cost per unit

Useful as a starting framework; in practice, supplier minimums, volume discounts, and storage constraints modify the calculated EOQ.

Reorder Points and Safety Stock

A reorder point is the on-hand quantity at which you trigger a new purchase order, calculated as:

> Reorder Point = (Average Daily Sales × Lead Time in Days) + Safety Stock

Safety stock covers demand spikes and supplier delays during the replenishment window. The amount depends on how much variability you're willing to absorb — more safety stock means fewer stockouts but higher carrying costs.

Inventory Management Best Practices

Set reorder points per SKU, per warehouse. A blanket "reorder when below 50 units" rule doesn't work for a catalog of 500 SKUs with different velocities, lead times, and storage locations. Per-SKU reorder points, reviewed seasonally, prevent both stockouts and overstock.

Cycle count instead of annual audits. Counting your entire warehouse once a year creates a single high-effort event that still leaves you with potentially stale counts for 364 days. Cycle counting — counting a rotating subset of SKUs continuously throughout the year — catches count drift early, before it causes fulfillment problems. Count A items most frequently.

Receive against purchase orders, not off a packing slip. Recording a receipt against an open PO creates a receiving record that ties physical counts to procurement decisions. It surfaces supplier discrepancies (short shipments, wrong items) and gives finance accurate landed cost data. Receiving by scanning items against the PO is faster and more accurate than manual entry.

Scan at pick and pack. Requiring warehouse staff to scan every item before a label prints catches the wrong item or wrong quantity before it ships. The cost of a mispick caught at the packing station is a ten-second scan. The cost of one caught by the customer is a return, a re-ship, and a service interaction.

Track inventory in one system, not across platforms. Each sales channel stores only its own counts — Shopify doesn't know about Amazon sales; Amazon doesn't know about eBay. Using platform-native inventory means manually updating counts after every sale. A central inventory system that syncs to all channels eliminates this reconciliation work and prevents oversells between channels.

Separate committed from available inventory. Physical on-hand is not the same as available to sell. Units allocated to open orders are committed — they can't be sold again. Tracking available on hand (physical on hand minus committed) is the number that should feed your channel listings.

Tie your PO workflow to inventory. Purchase orders that live in a spreadsheet separate from your inventory system mean receiving stock without automatically updating counts — and finance without accurate cost data. A PO workflow integrated with inventory means receipt = count update + cost record in one step.

Inventory Management KPIs

Inventory Turnover Ratio

> Annual COGS ÷ Average Inventory Value

How many times you sell and replace your inventory in a year. Higher turnover means you're not tying up capital in slow-moving stock. Benchmarks vary widely by category — perishables turn fast; furniture turns slowly.

Days Inventory Outstanding (DIO)

> (Average Inventory Value ÷ Annual COGS) × 365

The average number of days inventory sits before selling. Lower is generally better; too low suggests stockout risk.

Stockout Rate

The percentage of order lines that couldn't be fulfilled due to zero stock. Even a 1–2% stockout rate represents real lost revenue and customer friction.

Fill Rate

The percentage of order lines shipped complete on the first attempt. A fill rate below 95% typically indicates either forecasting problems or receiving/count accuracy issues.

Carrying Cost Percentage

> Total Annual Carrying Costs ÷ Average Inventory Value

Carrying costs include storage, insurance, capital cost, and shrinkage. For most businesses this runs 20–30%. If your carrying cost percentage is high, your reorder quantities may be too large or your slow-movers need to be liquidated.

Inventory Accuracy

> Counted Units ÷ System-Recorded Units (from cycle counts)

The gap between what your system says you have and what's physically there. Accuracy below 95% causes fulfillment failures and unreliable purchasing decisions.

Common Inventory Management Challenges

Multichannel overselling. Selling the same SKU on Shopify, Amazon, and eBay from a single inventory pool — without a system that shares and commits stock across channels — produces oversells as a matter of probability, not bad luck.

Supplier lead time variability. A supplier that averages 10-day lead time but sometimes ships in 7 and sometimes in 18 makes safety stock calculations harder. Tracking actual lead times per supplier, per PO, and adjusting reorder points seasonally reduces exposure.

Returns and reverse inventory. Returned goods that go back into available inventory without inspection inflate available counts and create fulfillment errors. A returns workflow that quarantines items before restocking — and logs every adjustment with a reason code — keeps counts clean.

Demand forecasting. Forecasting is hard. The minimum viable approach: segment SKUs by velocity, track seasonality year-over-year, and treat safety stock as your buffer against forecast error rather than trying to predict demand precisely. Reserve the analytical sophistication for A items only.

Kitting and bundling. Selling a bundle that uses components also sold individually creates a dependency: bundle availability depends on component stock, and component stock is affected by both individual and bundle sales. Without component-level tracking, overselling bundles — or selling a component needed for a bundle — is a consistent problem. See: Kitting and Bundle Inventory Management

Inventory Adjustments: What They Are and When They're an Expense

An inventory adjustment is a manual change to an on-hand count — correcting a discrepancy between what your system says you have and what's physically there. Whether an adjustment is an expense depends on *why* it's being made.

Adjustments that are not expenses correct the inventory asset account without creating a loss. These include cycle count corrections (the count was wrong, not the inventory), receiving discrepancies when stock is adjusted to match what actually arrived, and return processing when a customer return is added back to available stock.

Adjustments that are expenses reflect actual loss in value: damage write-offs (units destroyed or unsellable), theft and shrinkage, and obsolescence write-downs. These reduce the inventory asset and create a corresponding debit to COGS or a shrinkage loss account.

For operational purposes, a good inventory system logs every adjustment with a reason code so the accounting treatment can be determined correctly. In Ordoro, every adjustment requires a reason code (cycle count, damage, theft, supplier error, return received, production consumption) and is permanently logged with the quantity change, timestamp, and the user who made it. This audit trail answers the question that always follows a count discrepancy: *how did we get here?*

See: How do I adjust inventory in Ordoro?

Inventory Management Software vs. Spreadsheets

Spreadsheets work for a single-channel business selling a small catalog with simple fulfillment. The signs that you've outgrown them:

• You're selling on more than one channel and updating stock counts manually after each sale
• You've had an oversell — the same units sold twice, or orders you couldn't fulfill
• You've had a stockout you didn't see coming because a reorder point wasn't set or wasn't caught
• Receiving shipments requires a manual count entry in a separate file from your orders system
• Finance is asking for accurate COGS data you can't easily produce
• Your team has outgrown a single person managing inventory

Inventory management software centralizes all of this: stock counts update automatically as orders arrive and shipments go out; reorder points trigger purchase orders; receiving updates counts in real time; channels sync automatically.

For ecommerce businesses shipping from multiple warehouses, managing kits, or running dropshipping alongside first-party inventory, software isn't optional — the operational complexity is too high to track manually without consistent error.

See: Inventory Management Software for Ecommerce

Frequently Asked Questions

What is inventory management?

The end-to-end process of purchasing, receiving, storing, tracking, fulfilling, and replenishing goods — with the goal of maintaining accurate stock counts and meeting demand without stockouts or excess inventory.

Why is inventory management important?

Accurate inventory is the foundation of every downstream business function: fulfillment depends on knowing what's in stock; purchasing depends on knowing when to reorder; finance depends on accurate cost of goods sold. Poor inventory management causes stockouts (lost sales), oversells (cancelled orders), excess carrying costs, and unreliable financial reporting.

What are the main inventory control methods?

FIFO (First In, First Out), LIFO (Last In, First Out), Weighted Average Cost, ABC analysis, Just-In-Time (JIT), and Economic Order Quantity (EOQ). Most ecommerce businesses use FIFO for depletion order, WAC for costing, and ABC analysis for prioritizing which SKUs get the most management attention.

What is ABC analysis in inventory management?

A method of segmenting your SKU catalog by revenue contribution and sales velocity — A items (high value, high velocity) get tight reorder points and frequent counts; C items (low value, slow-moving) get minimal attention and are candidates for liquidation. The goal is focusing operational effort where it has the most impact.

What is the inventory management process?

The cycle: forecast demand → create purchase orders → receive against POs → store in assigned locations → pick and pack orders → ship and push tracking → sync updated counts to channels → trigger replenishment when reorder points are hit.

What are inventory management best practices?

Set per-SKU reorder points; cycle count continuously rather than auditing annually; receive against purchase orders to maintain a receiving record; scan at pick and pack to prevent mispicks; track committed vs. available inventory; use one system of record shared across all channels.

What does inventory management cost?

The cost of inventory management software varies by platform and order volume. The more relevant cost is the carrying cost of your inventory — typically 20–30% of its value annually — which good inventory management reduces through tighter reorder quantities and fewer slow-movers. See: Ordoro pricing

What is lead time in inventory management?

The time between placing a purchase order and receiving the goods. Lead time determines how early you need to reorder — a supplier with a 14-day lead time requires triggering a PO when stock falls below 14 days of sales velocity, plus safety stock. Tracking actual lead times per supplier, per order, is the input to accurate reorder points.

Example: a product sells 100 units per day, lead time is 10 days, and you hold 200 units of safety stock. Reorder point = (100 × 10) + 200 = 1,200 units. When on-hand hits 1,200, place the next PO.

What is the difference between lead time and delivery time?

Lead time covers the full period from placing an order to receiving stock — including supplier processing, manufacturing (if applicable), and shipping. Delivery time refers only to the transit portion after the order leaves the supplier. A 12-day lead time might include 3 days of supplier processing and 9 days of shipping; delivery time in that case is 9 days. For reorder point calculations, use lead time, not delivery time.

What is an example of an inventory management system?

A business selling on Shopify, Amazon, and eBay uses Ordoro as its inventory management system. All three channels connect to Ordoro, sharing one inventory pool. When an Amazon order arrives, Ordoro commits those units immediately, so the same stock can't sell on Shopify before the next sync. When stock falls to a reorder point, a purchase order goes to the supplier. When the shipment arrives, staff scan items against the PO to receive them — counts update automatically. When orders ship, tracking posts back to each channel. See: How Ordoro manages multichannel inventory

What are the functions of inventory management?

Demand planning and forecasting; supplier and purchase order management; receiving and goods-in; storage and location management; order allocation and fulfillment; returns and adjustments; reporting and costing. Each function feeds into the others — accurate receiving feeds accurate counts; accurate counts feed accurate fulfillment; accurate fulfillment feeds accurate financial reporting.

What are the benefits of inventory control?

Fewer stockouts and oversells; lower carrying costs through tighter reorder quantities; faster fulfillment through organized storage and accurate pick lists; accurate financial data for COGS and margin calculations; visibility into supplier performance; a foundation for scaling without proportionally increasing headcount.

Can I make an inventory adjustment without expensing it?

Yes. Not every inventory adjustment is an expense. Adjustments that correct counting errors — cycle count reconciliations, receiving discrepancies, unit-of-measure fixes — update your inventory asset account without creating a P&L entry. Adjustments that reflect an actual loss (damaged goods write-offs, theft, obsolescence) are expensed: debit a shrinkage or loss account, credit Inventory. The reason code you assign to each adjustment determines its accounting treatment. See the Inventory Adjustments section above for the full breakdown.

What is the difference between a perpetual and periodic inventory system?

A perpetual inventory system updates stock counts in real time with every transaction — each sale, receipt, and adjustment immediately changes the on-hand number. Inventory management software operates on perpetual tracking. A periodic inventory system updates counts at fixed intervals (weekly, monthly, annually) by physically counting stock. Periodic systems are simpler but leave you with stale counts between audits — a problem for any business with meaningful order volume or multiple channels. Most ecommerce businesses with more than a few hundred orders per month need perpetual tracking to prevent oversells and fulfillment errors.

What does JIT mean in inventory?

JIT stands for Just-in-Time. It's an inventory strategy where you order and receive goods as close as possible to when they're needed, minimizing stock held on hand at any time. JIT reduces carrying costs and storage requirements but increases exposure to supply chain disruptions — any delay from a supplier halts production or fulfillment. It works best when supplier lead times are reliable and demand is predictable. In practice, most businesses implement JIT principles by tightening reorder points and reducing safety stock on slow-moving SKUs rather than eliminating buffer stock entirely. See: JIT Inventory Management in CPG

What is LIFO in inventory management?

LIFO stands for Last In, First Out — a costing method where the most recently received stock is recorded as sold first. During inflationary periods, LIFO increases COGS and reduces taxable income, which is why some businesses use it for accounting purposes. LIFO is not permitted under IFRS and is rare for ecommerce businesses; most use FIFO (oldest stock sold first) or Weighted Average Cost instead.

What is the cost of goods sold formula?

COGS = Beginning Inventory + Purchases During the Period − Ending Inventory. It represents the direct cost of products sold in a given period. For businesses using Weighted Average Cost (WAC), the per-unit cost is the blended average across all units in inventory, updated with each new supplier receipt. Accurate COGS depends on accurate inventory counts — if your ending inventory count is wrong, your COGS figure is wrong.

What are raw materials in inventory management?

Raw materials are unprocessed inputs used to manufacture finished goods — components, ingredients, packaging, or base materials that become part of the final product. In inventory management, raw materials are tracked separately from work-in-progress (WIP) and finished goods. For businesses that manufacture or assemble products, raw material inventory levels directly affect production capacity. Ordoro's Bill of Materials feature links finished good SKUs to their component raw materials, consuming the correct quantities from inventory when a manufacturing order completes. See: Manufacturing Inventory Management

What does SKU mean?

SKU stands for Stock Keeping Unit. It's a unique alphanumeric identifier assigned to each distinct product variant — size, color, configuration — that you track as a separate inventory item. If you sell a shirt in three colors and three sizes, you have nine SKUs. SKUs are internal identifiers you define yourself; they don't follow any external standard. Every inventory system, channel listing, and purchase order line references a SKU. Consistent SKUs across all systems — Shopify, Amazon, your warehouse — are what allow multichannel inventory sync to work correctly.

What is a UPC code?

A UPC (Universal Product Code) is a standardized 12-digit barcode identifier used to identify products across different retailers and systems. Unlike SKUs (which you define internally), UPCs are issued through GS1 and are consistent regardless of which retailer or system scans them. Amazon and most major marketplaces require UPCs to list products. UPCs are scanned at receiving and pick/pack in warehouse workflows — Ordoro supports barcode scanning for both. See: Inventory App With Barcode Scanner

What does MOQ mean?

MOQ stands for Minimum Order Quantity — the smallest number of units a supplier will sell in a single purchase order. MOQ is set by the supplier, not the buyer. High MOQs require larger upfront inventory investments and increase carrying costs for slow-moving SKUs. When calculating reorder quantities, MOQ is a practical constraint on the EOQ formula — if your optimal order quantity is 80 units but your supplier's MOQ is 200, you order 200. Negotiating lower MOQs is part of supplier management, particularly as your purchasing volume grows.

What is FIFO in inventory management?

FIFO stands for First In, First Out. It means the oldest stock is sold and depleted first. For most physical goods — especially perishables, apparel, or anything with a shelf life or model year — FIFO prevents holding old inventory past its useful life and reduces obsolescence risk. It is the most common inventory costing and depletion method for ecommerce businesses. See the Inventory Control Methods section above.

What does "cost of goods" mean?

"Cost of goods" typically refers to the direct cost of the products a business buys or manufactures for resale — the purchase price from suppliers, plus any costs directly tied to getting the goods ready to sell (freight, duties). It is closely related to Cost of Goods Sold (COGS), which is the portion of that cost attributable to goods actually sold in a period. The distinction: cost of goods is the value of your inventory asset; COGS is what flows to the income statement when that inventory sells.

What is the AOV formula?

AOV stands for Average Order Value. The formula is: AOV = Total Revenue ÷ Number of Orders. For example, $50,000 in revenue across 500 orders = $100 AOV. AOV is an ecommerce performance metric rather than an inventory metric, but it connects to inventory decisions — higher AOV often correlates with bundle or kit strategies, upsells, and minimum order thresholds that affect how you stock and fulfill.

What is a backorder?

A backorder occurs when a customer places an order for a product that is currently out of stock — the order is accepted but fulfillment is delayed until inventory is replenished. Backorders are distinct from stockouts in that the sale is captured rather than lost. Managing backorders requires clear customer communication, accurate restock ETAs, and a fulfillment queue that prioritizes backorder fulfillment when new inventory arrives. The best way to prevent backorders is accurate reorder points and safety stock — triggering replenishment before stock hits zero rather than after.

What does ERP stand for?

ERP stands for Enterprise Resource Planning. An ERP is a broad software system that integrates multiple business functions — accounting, HR, procurement, manufacturing, and inventory — into a single platform. Examples include NetSuite, SAP, and Microsoft Dynamics. For most ecommerce businesses, a full ERP is more than necessary. A dedicated inventory management platform like Ordoro handles the operational layer (inventory, orders, fulfillment) while accounting software like QuickBooks handles the financial layer — without the implementation cost and complexity of an ERP. ERPs become relevant when a business needs to unify manufacturing, finance, and operations at significant scale. See: Inventory Control Software QuickBooks