How to Track Cost of Goods Sold in an Inventory Business: The Complete Picture
Cost of Goods Sold (COGS) is the number that separates revenue from gross profit on your income statement. It's also one of the most misunderstood figures in inventory business accounting.
Many business owners think COGS equals what they paid for goods this month. It doesn't. COGS is the cost of goods that were sold this month — which could include inventory purchased months ago. The difference matters a lot.
What COGS Is (and What It's Not)
COGS is: The cost of the specific inventory units that were sold during a period. It's calculated from your inventory records based on your costing method (FIFO or weighted average).
COGS is not:
- What you spent on inventory this month (that's inventory purchases)
- Your total supplier spend
- The purchase price of inventory you ordered but haven't received
- A cash-based measure
This distinction is fundamental and frequently confusing. You might have paid Rs. 15,00,000 for inventory this month, but if you only sold Rs. 8,00,000 worth (at cost), your COGS is Rs. 8,00,000. The remaining Rs. 7,00,000 is sitting in inventory on your balance sheet, not in COGS.
Conversely, you might sell Rs. 20,00,000 of inventory (at cost) this month while only purchasing Rs. 5,00,000 of new inventory — because you're selling from existing stock.
The COGS Calculation
COGS = Opening Inventory + Purchases − Closing Inventory
This is the periodic calculation. It's why you need accurate opening and closing inventory values (from physical counts or perpetual records) to calculate COGS correctly.
Example:
- Opening inventory: Rs. 40,00,000
- Plus: purchases this month: Rs. 15,00,000
- Less: closing inventory: Rs. 35,00,000
- COGS = Rs. 20,00,000
In a perpetual inventory system (which your inventory management software provides), COGS is calculated in real time with each sale — the system knows the cost of each unit sold based on the inventory cost layers.
What Goes Into COGS for Imported Goods
If you're sourcing goods internationally, COGS should reflect landed cost, not just purchase price.
When you calculate the cost of goods sold, each unit's cost should include:
- Purchase price per unit
- Pro-rata share of freight
- Pro-rata share of import duties and taxes
- Pro-rata share of clearance and handling
If you're recording inventory at purchase price and treating freight and duties as separate operating expenses, your COGS is understated and your gross margin is overstated. This is a common error that makes businesses think they're more profitable than they are.
COGS in Manufacturing: Adding Production Costs
For manufacturers, COGS is more complex than for distributors. The cost of a finished product includes:
Direct materials: Raw materials and components that go into the product, at their purchase (landed) cost.
Direct labor: The labor cost directly attributable to producing the unit — wages for production staff, calculated per unit produced.
Manufacturing overhead: Costs that are part of production but can't be directly attributed to individual units — factory rent, equipment depreciation, utilities. These are allocated to products using a overhead absorption rate.
Total product cost = Direct materials + Direct labor + Manufacturing overhead
This full cost is what flows into COGS when the finished goods are sold. Manufacturing businesses that only track material cost in COGS are understating their cost of production.
Why Gross Margin Analysis Matters
Your gross margin — the percentage of revenue remaining after COGS — is the operational leverage measure of your business.
By product category: Different products have different gross margins. If you're selling Product A at 35% margin and Product B at 12% margin, knowing this changes your sales priority, pricing strategy, and marketing investment.
By customer: Customers who frequently order small quantities, request custom packaging, or require high service levels cost more to serve. Your effective gross margin by customer, after accounting for these service costs, can differ significantly from the headline product margin.
Over time: Is your gross margin expanding or contracting? Contraction without a known cause (input cost increases, pricing pressure) is a signal worth investigating. It could be mix shift, shrinkage, or a COGS calculation error.
Common COGS Errors
Recording all supplier spend as COGS immediately. When you receive goods, they become inventory (an asset). They become COGS only when sold. Expensing all purchases as COGS overstates your expenses in buying periods and understates them in selling periods — making your profitability picture lumpy and inaccurate.
Not including landed costs. As above — undervalued inventory means understated COGS when those units eventually sell.
Wrong inventory count at period-end. Because COGS = Opening + Purchases − Closing, an inaccurate closing count produces an inaccurate COGS. A count that's too high makes COGS look too low (better margin than reality). A count that's too low makes COGS look too high (worse margin than reality).
Not reversing returns correctly. When goods are returned, the sale is reversed and the inventory should be reinstated. If the inventory return isn't recorded, COGS stays overstated and inventory stays understated.
Not accounting for write-offs separately. When inventory is written off, it leaves inventory as a loss — not as COGS. Bundling write-offs into COGS misrepresents both your trading margin and your exceptional losses.
The Financial Reporting Connection
COGS drives gross margin, which is the headline performance measure for any product business. But it's only as reliable as the inventory data it's derived from.
When your inventory management and accounting are in the same system, COGS is calculated automatically and continuously — every sale creates the correct COGS entry, every receipt updates the inventory cost layers, and your gross margin at any point in the month reflects the actual trading performance to date.
When inventory and accounting are separate systems, COGS is calculated at period-end from reconciled inventory counts — which introduces timing lags and reconciliation errors.
Sevenledger calculates COGS in real time from your inventory movements — so your gross margin is always current, your financial reporting is always accurate, and your accounting closes clean.