COGS vs. Expenses: The Bookkeeping Mistake That Costs Resellers Real Money

Here is a bookkeeping mistake that shows up in almost every reseller's first year, costs real money, and is completely invisible while you are making it: treating the money you spend on inventory as an expense in the month you spend it. It makes your monthly numbers nonsense, and at tax time it can mean deducting the same dollar twice.

Two kinds of spending

Money leaving your business splits into two categories that behave very differently.

Operating expenses are the cost of being in business at all: booth rent, mileage, supplies, fees, marketing. You spent it, it is gone, and it comes off in the period you spent it.

Cost of goods sold is what you paid for the specific things you sell. It does not come off when you buy the item. It comes off when the item sells — matched against the money that item brought in.

The $12 lamp on your shelf is not an expense. It is $12 of value you are holding, and it becomes a cost at the moment it turns into a sale.

Why it matters month to month

Suppose you spend $900 at auction in March and sell most of it over April, May, and June.

Booked as an expense, March is a disaster and the spring looks like a windfall you cannot explain. Neither month tells you anything true. You cannot see whether the auction was a good buy, whether your pricing is working, or whether the booth is carrying itself, because the cost and the revenue are in different months.

Booked as inventory, each item carries its own cost until it sells. Then April shows what April actually earned: revenue, minus what those specific pieces cost you, minus that month's rent and gas. That number is worth acting on.

The double-count trap

This is the version that costs money at tax time. A reseller buys a $300 lot, logs it as a purchase expense, then also records each item's cost as they enter them into inventory. When the items sell, those per-item costs come off again as cost of goods sold.

The same $300 has now been deducted twice. It looks generous until someone asks, and then it is an underpayment with your name on it.

The rule is simple: if an item has a cost recorded against it, that money must not also sit in your expense totals. Pick one place for each dollar. A lot buy you never broke into individual items can reasonably live as a purchase; a lot you costed out item by item belongs in inventory only.

A worked example

You pay $240 for a box of twenty pieces at auction and split it evenly — $12 each. Booth rent is $250 for the month, and you drove 40 miles to collect it.

In one month you sell six of them for $47 each, or $282.

• Revenue: $282
• Cost of goods sold: 6 × $12 = $72 — only the six that sold
• Gross profit: $210
• Operating expenses: $250 rent, plus the mileage
• Result: a small loss for the month, with $168 of inventory still on the shelf

Booked the wrong way — the whole $240 as a March expense — March shows a $208 loss and April shows pure profit with no cost at all. Same money, same items, and a picture that would lead you to the wrong decision in both months.

The awkward part: unsold inventory

The corollary catches people out. If you spent $4,000 on stock this year and half of it is still sitting in your booth on December 31, you do not get to deduct $4,000. You deduct what sold. The rest is still inventory, and it carries into next year.

This is why a heavy sourcing year can produce a tax bill that feels disconnected from your bank balance: the money is gone, but it is sitting on a shelf rather than showing up as a deduction. Knowing that in advance is the difference between planning for it and being blindsided.

How to keep it straight

• Put a cost on every item as you enter it. Even a rough per-item split of a lot is far better than nothing.
• Keep purchases and operating costs in separate columns from the first entry.
• When you split a receipt into items, take that money out of your expense total. This is the exact point the double-count happens.
• Look at your unsold inventory value before year end, while there is still time to do something about it.

None of this needs an accounting background. It needs each dollar to have exactly one home, decided at the moment you record it rather than reconstructed in April.

General information, not tax advice. Inventory accounting has real rules and some genuine options depending on the size and structure of your business — worth a conversation with a tax professional.