Cost of goods sold: what goes in it, and why the answer changes your margin

Cost of goods sold is the direct cost of what you actually sold in a period. Not what you bought, not what is sitting in the stockroom — what left. That distinction is the whole of the calculation, and it is why the formula involves opening and closing stock rather than a simple total of purchases.

The number matters because everything above it and below it is judged against it. Gross margin is revenue minus this figure; profitability comparisons across periods are meaningless if the contents of the line shift. And they do shift, quietly, whenever somebody decides that delivery or packaging belongs somewhere else.

The calculation

1. Opening stock at the start of the period, at cost.
2. Plus purchases during the period, including inbound freight and duty — the cost of getting goods to you is part of what they cost.
3. Minus closing stock at the end of the period, at cost.
4. The result is cost of goods sold. If it looks wrong, the stock figures are usually the reason: a count that never happened, or one done on a different basis at each end.

For a service business the equivalent is cost of sales: the labour delivering the work, plus anything bought specifically for it. The mechanics differ, the principle does not — direct costs of what was delivered, and nothing else.

What belongs in it

• Purchase or manufacturing cost of the goods.
• Inbound freight, duty and import charges.
• Packaging that goes to the customer with the product.
• Direct labour where you manufacture or where staff time is tracked to jobs.
• Payment processing fees, arguably — many small businesses put them here and it is defensible, provided it is consistent.
• Not: rent, salaries of people not delivering the work, marketing, software, insurance, outbound delivery in most treatments. Those are operating expenses below the gross margin line.

The consistency matters more than the classification. Reasonable businesses disagree about whether outbound delivery sits in cost of goods sold or in operating expenses, and either answer works — as long as it is the same answer every month. A business that reclassifies mid-year produces a margin change that looks like a commercial trend and is an accounting decision, and that misreading has led people to celebrate or panic about nothing.

Where it goes wrong

• No stock count. Without opening and closing figures the calculation is a guess, and the guess always flatters the period it is made in.
• Counting purchases instead of sales. Buying six months of stock in March does not make March unprofitable, though it will look that way.
• Ignoring stock that will never sell. Obsolete or damaged inventory sitting in the closing figure overstates both the asset and the profit, and the correction always arrives eventually.
• Mixing bases — counting at cost one period and at selling price the next, or including duty at one end and not the other.

What to do with the number

Divide it into revenue and you have gross margin, which is the number that decides what the business can afford — covered in gross margin. Track it per product line and the picture usually changes: most businesses have a line they sell enthusiastically at a cost they have never actually calculated. And watch the ratio of stock to cost of goods sold over time, because rising stock against flat sales is working capital quietly disappearing into the stockroom, which is the ground covered in working capital.

What remains on the shelf decides what was charged against sales. Inventory valuation sets that figure, and the method chosen moves reported profit without anything physical changing.

Where it comes from

Ettex Books produces the figure from purchases and stock movements, provided both are recorded; the stock side sits in inventory management, and the wider statement it feeds into is profit and loss statement.

The limit worth naming: no software can decide what belongs in your cost of goods sold. That is a policy choice, and the value of making it explicitly is that next year's comparison means something.