Cost of goods sold (COGS) is the cost assigned to the goods a business sells during a reporting period. For purchased merchandise, that can include qualifying acquisition costs. For manufactured goods, it can also include conversion costs such as direct labor and production overhead under the applicable policy.
Buying inventory, paying a supplier and recognizing COGS are different events. A buyer influences purchase quantities and costs; finance determines the cost assignment, classification and recognition in the accounts.
The simplified COGS formula
For a trading-stock example with no separately classified losses, transfers or other adjustments:
COGS = opening inventory at cost + net inventory purchases − closing inventory at cost
Use consistent dates, units, ownership scope and valuation. Net purchases should reflect relevant returns, allowances and acquisition charges under the accounting policy. It is not simply the total of supplier payments during the period.
A production business needs the relevant raw-material, work-in-progress and finished-goods flows as well as conversion costs. Do not apply a merchandise-purchases-only formula to a factory and assume it captures the full result.
A worked example
Assume a fictional retailer starts a month with $20,000 of inventory at cost. It acquires $15,000 of goods, receives $1,000 of purchase returns or allowances, and incurs $600 of eligible inbound freight. Closing inventory is $18,000 on the same cost basis. There are no other inventory movements or losses in this example.
Net inventory purchases = $15,000 − $1,000 + $600 = $14,600
Goods available at cost = $20,000 + $14,600 = $34,600
COGS = $34,600 − $18,000 = $16,600
If net revenue is $30,000, gross profit is $13,400 and gross margin is approximately 44.67%. A supplier payment made next month does not, by itself, move this month's sold-goods cost into next month's COGS under an accrual inventory model.
The IFRS Foundation's IAS 2 summary explains qualifying inventory costs and recognition when the related goods are sold under IFRS. Apply the accounting framework relevant to the business, including its treatment of losses and write-downs.
Purchases, inventory and COGS
Suppose 100 interchangeable units are purchased at $10 and 40 are sold, with no other stock, charges or adjustments. In this simple example, $400 is assigned to goods sold and $600 remains in inventory. Paying the full $1,000 invoice does not make all $1,000 COGS immediately.
If another receipt has a different unit cost, the chosen cost-flow method affects the amounts assigned to sold and remaining units. FIFO and other cost-flow assumptions and weighted average cost explain those calculations. Physical picking order and accounting cost assignment need not be identical.
COGS vs operating expenses and food cost
COGS is not defined merely as “variable cost,” and operating expenses are not all fixed. Production overhead can be included in inventory cost, while selling commissions can vary with sales and remain a selling expense under the relevant policy.
Restaurants often track food and beverage cost separately from labor and other operating costs. An ingredient-only food-cost measure is useful for kitchen decisions, but its scope is not automatically identical to a manufacturer's or another business's reported COGS. Label what each report includes before comparing percentages.
There is no universal good COGS percentage. Review cost classification, product mix, selling prices and the remaining costs that gross profit must cover.
Counts, shrinkage and receipt discrepancies
An unrecorded shortage can leave recorded closing inventory overstated. In the simplified periodic formula, an overstated closing balance understates the balancing cost. A corrected count reveals the missing value, but it does not prove that all of it was sold normally. Finance must determine whether it belongs in COGS, an inventory-loss account or another category under the policy.
Likewise, receiving 92 of 100 ordered units does not automatically make the buyer owe the price of all 100 or make COGS per unit rise. Record the actual receipt, retain the outstanding or disputed balance, and resolve the supplier invoice or credit. Some shared acquisition charges may still apply; allocate them under a documented policy.
Keep physical quantity, supplier liability and inventory valuation distinguishable. Three-way matching supplies relevant comparison evidence, while authorization, coding, tax and payment checks remain necessary.
How procurement influences the inputs
Supplier prices, freight, discounts, accepted substitutions and purchase quantities affect acquisition economics. A changed quote is an early planning signal; it is not automatically an accepted transaction or recognized expense.
For a recipe or BOM, verify the quantity and yield basis. If a finished portion needs 200 grams of usable input and the process yields 75% of purchased weight, the theoretical purchase requirement is 200 / 0.75 ≈ 266.7 grams per portion. That is a planning conversion, not a complete COGS calculation. Avoid adding the same yield loss again as an independent waste allowance.
Use purchase price variance with a defined baseline. A difference from a standard cost can exist even when the supplier invoices exactly the accepted PO price. A supplier billing exception and an accounting variance answer different questions.
Preserve the evidence through accounting handoff
Keep the original PO, supplier proposals, buyer-approved revisions, receipts, additional charges and credits connected. A living purchase order makes that history easier to inspect when a cost changes.
LineNow's procurement workflow supports that purchasing record and accounting handoff. Demonstrate a partial receipt, a late freight charge and a supplier credit. Confirm how the relevant finance system values inventory and recognizes COGS; an operational item-cost record or exported bill is not by itself a complete COGS ledger.
Keep manual review and exceptions visible where the workflow requires them.