Profit per product: the Amazon best-sellers that lose you money

Ask a founder which Amazon product matters most and they will usually name the best-seller. Ask which product makes the most money and the room goes quiet, because the account reports sales, not profit, and the two are often different lists.

“Profit, not sales” is the problem brands bring us more than any other: margins that have thinned, TACoS that has crept up, and ad spend that grows without the sales to match. Profit per product is one of the checks we run whenever we have a brand’s Seller Central data. The finding we are looking for is a product that sells well and loses money.

This guide shows you how to find those products yourself. Every fee and report name below was read on Amazon’s UK pages on 26 October 2026.

The sum, one product at a time

Account-level profit hides the answer. A healthy total can be three good products paying for one bad one. So run the sum for each product (each child ASIN, if your variations have different costs):

Two lines need care, because Amazon uses two price bases:

• The referral fee is charged on the price including VAT. Amazon calculates it on a total that includes “any taxes and customs duties"¹³. The UK fee schedule sets it at 15% with a £0.25 minimum in most categories, including Toys and Games, Sports and Outdoors and Kitchen¹. On top, “A 2% digital services fee will apply on Selling on Amazon and FBA fees for sales in our UK… stores"¹.
• Advertising is reported without VAT. Amazon Ads says: “Attributed sales don’t include tax. Inclusive tax such as VAT is subtracted from sales totals.“¹⁰ At the UK standard rate of 20%¹¹, VAT is one-sixth of a VAT-inclusive price.

So work out margin, ACoS and TACoS on the ex-VAT price, and fees on the VAT-inclusive one. Our Amazon seller fees guide covers every fee line in detail, and the FBA fees guide covers every size tier.

Where each number lives in Seller Central UK

You don’t need a tool to start. Every line of the sum has a report.

Amazon also has its own tool for this. Profit analytics “combines sales, returns, fees, ads and seller provided cost data to help you analyse profitability at the SKU, ASIN and parent-ASIN level"⁶. It is a good place to start, with one warning from Amazon itself: its net proceeds figures “are only estimates and are dependent on seller provided inputs, such as inbound shipping and cost of goods sold"⁶. If you haven’t loaded your own costs, it can’t tell you which products pay.

One trap in the advertising line: for sellers, Amazon credits an ad with sales of the “products featured in the ads as well as any other products sold by the Seller Central merchant"¹⁰, and the advertised product report has a separate column, Sales (halo), for sales “where the purchased SKU was other than the one advertised"⁹. When you charge ad spend to a product, charge what was spent advertising it, and judge it against that product’s own sales.

A worked example: three products, one surprise

Here is an illustration with invented figures: a brand selling three FBA products in categories that pay a 15% referral fee, priced above £20 so none qualifies for low-price FBA. The fees use the non-peak rates that return on 15 January 2027², with the fuel and logistics surcharge at 2%, the rate from 2 November 2026³. During the festive peak, A’s fee is £3.38 before the surcharge², or £3.45 with it, so A loses about 12p more per unit until 14 January 2027.

• Product A, the best-seller: £24.99, 2,000 units a month. A standard parcel up to 1.40 kg: £3.26 before the surcharge².
• Product B, the steady one: £29.99, 900 units a month. A small parcel up to 400 g: £3.00².
• Product C, the quiet one: £39.99, 350 units a month. A small parcel up to 900 g: £3.04².

Storage, cost of goods, returns, other costs and advertising are invented. To check one column: for A, £24.99 − £4.17 − £3.75 − £3.33 − £0.14 − £0.29 − £7.50 − £0.60 − £0.35 = £4.86, and £4.86 − £5.40 = −£0.54.

Now the month:

The best-seller brings in more than half the sales and is the only product losing money. The product at the bottom of the sales report makes nearly as much as the middle one. Sort this account by sales and you would protect A and ignore C. Sort it by profit and you would do the opposite.

Why A loses money

A keeps £4.86 a unit before advertising. On its ex-VAT price of £20.82, that is a margin of 23.3%. It spends 25.9% of its ex-VAT sales on ads. Our break-even ACoS guide gives the rule: profit after advertising = sales × (margin − TACoS). For A, that is £20.82 × (23.3% − 25.9%), a loss of about 54p a unit.

This is how best-sellers go wrong. A product sells, so it gets more budget. The extra spend buys sales at a falling return, and nobody checks the product’s own profit because the account total still looks fine. Our TACoS guide shows how to set a ceiling for each product group so it can’t drift past its margin.

What to do with each product

A loss-maker needs a diagnosis before a fix. Look at where its money goes, then pick one change, measure it for a month, and only then try the next.

Cut the ads: when it makes money before advertising

A makes £4.86 a unit before ads, so the product works. The ad spend doesn’t. Start with search terms that spend and never sell, then bids on terms where its ACoS is above its 23.3% break-even.

How many units you lose when you cut spend depends on how much of the product’s sales the ads were really creating. Measure it; don’t assume it. On one account we manage, TACoS fell from about 45% to 14% within about six weeks, while weekly sales kept rising.

Reprice: when the price is the problem

If a product sells easily and its margin is thin before advertising, test a higher price. At £26.99 instead of £24.99, A’s VAT rises to £4.50 and its referral fee to £4.05, while the FBA fee stays at £3.33 and the digital services fee rises to £0.15. Profit before ads goes from £4.86 to £6.22, a gain of £1.36 a unit before any change in units or ads.

Price changes can cost conversion, so watch the unit session percentage in Business Reports for the weeks after. Our guide to Amazon sales falling on last year shows how to split a change into traffic, conversion and price.

Change the size band: when fulfilment is the problem

Amazon charges FBA by size tier and weight. A small parcel must be within 35 × 25 × 12 cm, a standard parcel within 45 × 34 × 26 cm². Product A ships as a standard parcel up to 1.40 kg at £3.26; if smaller packaging brought it into the small parcel tier, the same weight band costs £3.05². With the surcharge, that saves about £0.21 a unit ((£3.26 − £3.05) × 1.02), roughly £430 a month at 2,000 units.

That alone won’t rescue A, which is why it is a separate test rather than a fix to add on top of the others. On a product with a thin but positive margin, packaging changes like this often decide whether it pays. Our FBA fee and profit calculator shows the fee for each size and weight.

Bundle: when the price is too low to carry the fees

Cheap products pay a fulfilment fee on every unit, whatever the price. If a low-priced product is often bought with another, a bundle spreads one shopper’s order across a higher price. Amazon’s virtual product bundles tool lets Brand Representatives and Authorised Resellers combine “two to five complementary ASINs” on one detail page. The products must be in Brand Registry, have active FBA stock in “New” condition, and share the same fulfilment type¹².

Stop reordering: when nothing else works

Some products lose money before a penny of advertising. If repricing, packaging and a cheaper supplier can’t change that, the honest answer is to sell through the stock you have and not reorder. Before you do, check what the product does for the rest of the range: a product that brings in new customers who go on to buy others can be worth keeping at a small, deliberate loss. Decide that on purpose, with a budget and a review date, not by accident. Our guide to long-tail products covers when small sellers deserve a place in the range.

A monthly routine

Profit per product moves every month: fees change, storage charges land, ad costs drift. This is the routine we run.

Rerun it whenever Amazon changes a fee. Two are close: the festive peak fulfilment fee applies from 15 October 2026 to 14 January 2027², and “Starting 2 November 2026, the fuel and logistics-related surcharge will increase from 1.5% to 2%“³. Amazon says its Revenue Calculator, Profit Analytics dashboard and Fee and Economics Preview reports “have all been updated to reflect the peak rates and surcharge"³. Storage costs £0.76 per cubic foot a month from January to September and £1.51 from October to December for most standard-size products⁴, so slow sellers cost more to hold in the final quarter.

Keep the result on one page: product, units, sales, profit before ads, ad spend, TACoS, profit, and the one fix you are testing. Read it before you read the sales report. The Profit X-Ray runs the same sum across a whole account if you would rather start there.