Inventory Accounting and Cost of Goods Sold

01

Why cost per item is the foundation

A reseller with no reliable per-item cost cannot answer the questions that decide the business: which categories make money, which sourcing channels are worth the trip, whether a discount is affordable, what a bulk lot was really worth. They can only look at the bank balance, which conflates trading performance with purchasing timing and tells them nothing useful.

The consequences are specific and predictable. Sellers keep buying from a source that has been losing them money for a year. They discount into a loss because the margin they remember is the margin before fees. They believe a category is strong because it produces frequent sales, when it produces frequent sales at a cost that makes those sales pointless.

02

What belongs in the cost of an item

The purchase price is the obvious part. The rest is where sellers systematically understate their costs and overstate their margins.

Treatment varies by jurisdiction and by how your business is structured, and the boundary cases — particularly refurbishment materials and mileage — are worth a short conversation with an accountant rather than a guess. What matters here is that you make a consistent choice and apply it to every item, because a margin figure is only comparable against other margins calculated the same way.

03

Allocating the cost of a job lot

This is the part sellers find genuinely hard. You paid one price for forty items of wildly differing value, and now every one of them needs a number.

The wrong answer is dividing evenly. A box containing one item worth a great deal and thirty-nine worth very little will, under even allocation, show a spectacular margin on the good item and a loss on everything else — which inverts reality and will teach you exactly the wrong lesson about that source.

1. Estimate a realistic sale value for each item Based on recent completed sales, not asking prices. This is the same work as valuing inventory before you buy, so if you did it before bidding you already have the numbers.
2. Total those estimates This gives the lot's estimated retail value, which will be considerably higher than what you paid.
3. Take each item's share of that total An item estimated at a tenth of the lot's value carries a tenth of the lot's cost. This is proportional allocation, and it is the standard approach.
4. Spread the acquisition extras the same way Buyer premium, collection cost, and fuel ride along on the same proportions.
5. Assign a nominal cost to the worthless remainder Items you will scrap or donate carry effectively nothing, which is honest — they were not what you paid for.
6. Record it once and do not revisit it Retrospectively adjusting cost to flatter a sale defeats the entire purpose of measuring.

This takes a few minutes per lot and is the difference between knowing which of your sources are worth returning to and merely feeling that some of them are. It also directly improves your bidding, because it produces a record of what lots from each seller actually yielded — the discipline described in buying collections and job lots.

04

Timing: why unsold stock is not an expense

The most common misunderstanding in reseller bookkeeping is treating stock purchases as an expense in the month they were bought. They are not. Buying stock converts one asset — cash — into another — inventory. Nothing has been spent in the profit-and-loss sense until the item sells.

Get this wrong and the numbers become actively misleading in both directions. A month with heavy buying looks like a disaster. The following month, when that stock sells with no recorded cost against it, looks like a triumph. Neither reflects how the business traded, and a seller reading those figures will conclude that they should buy less in good months, which is precisely backwards.

05

The record that makes it work

The system does not need to be sophisticated. It needs to be complete, kept at the moment of purchase, and consistent. A record per item, carrying a small set of fields:

• A unique identifier that stays with the item physically, so the shelf and the record cannot drift apart.
• What it is, in enough detail to identify it a year later without holding it.
• Allocated cost, as calculated above.
• Purchase date and source, which turns your records into a supplier performance history.
• Where it is, because unfindable stock is functionally sold at zero.
• Listed date and channels, which produces your time-to-sell measurement.
• Sale price, channel, fees, and postage, completing the picture.

With those fields you can answer, without estimating: true margin per item after all costs, margin by category, margin by source, average days to sell, and the current value and age profile of everything on the shelf. Without them, all of those questions are answered by impression, and impressions in reselling are shaped by memorable wins rather than by the ordinary items that make up most of the volume.

Keeping this current across several sales channels is the point at which manual spreadsheets tend to fail — not because the arithmetic is hard, but because the update has to happen every time anything changes anywhere. Instica maintains one record per item across the channels it is listed on, so cost, status, and location stay attached to the item rather than being reconciled after the fact.

06

Reading the numbers once you have them

Good records are worth nothing unless they change decisions. A few readings do most of the work.

• Margin after everything, by category. Not gross margin. The figure after fees, postage, packaging and returns. Categories reorder dramatically under this lens, and the surprise is usually that high-ticket low-volume beats the reverse.
• Return on capital, not margin percentage. An item at a modest margin that turns in three weeks outperforms a strong margin that takes a year. This is the number that connects to cash flow, and it is the one most sellers never calculate.
• Yield by source. Total realised from a source against total paid, including the items that never sold. This is how a well-liked supplier is revealed to be unprofitable.
• Age profile of the shelf. Value held over ninety, one hundred and eighty, three hundred and sixty-five days. A worsening trend precedes a cash squeeze reliably enough to act on.
• Sell-through by category, which should be feeding directly back into what you buy.

None of this requires an accounting qualification. It requires that cost was recorded at the moment of purchase, allocated honestly, and left alone afterwards — and that discipline, more than any pricing tactic, is what separates sellers who compound from sellers who stay busy.