Selling on Amazon FBA: The Fee Stack Is the Business Model

Fulfilment by Amazon is not a side hustle. It is a stock business with a logistics provider attached, and whether it works comes down to arithmetic you can do before spending anything: what comes out of each sale before you see a penny.

What FBA actually is

You send inventory to Amazon's warehouses. Amazon stores it, picks and packs orders, ships them, handles customer service and processes returns. You handle sourcing, pricing and the decision about what to stock.

The trade is straightforward: you give up margin and gain logistics you could not build, plus eligibility for the delivery promise that a large share of buyers filter on.

The alternative, fulfilling yourself, keeps the margin and requires you to pick, pack, ship and handle returns to a standard the platform enforces. Neither is obviously right; they suit different products and different volumes.

The fee stack, in the order it hits

A referral fee on every sale, a percentage of the total including shipping, varying by category. This is charged whether you use FBA or not. It is the cost of selling on the marketplace at all.

A fulfilment fee per unit, set by size and weight bands. The bands are the thing to understand, because a product marginally over a threshold costs materially more to ship, and product design or packaging can move it back.

Storage fees, charged monthly by volume and higher in the run-up to Christmas. Slow-moving stock accrues these continuously, and long-term storage surcharges apply to inventory that sits.

Returns processing, which in some categories means paying to have a returned item handled and possibly disposed of. And then advertising, which is not a fee but is close to unavoidable for a new listing.

The arithmetic to do before buying stock

Take the realistic selling price. Subtract the referral fee, the fulfilment fee for the actual size band, an allowance for storage over your expected sell-through period, a returns allowance based on the category, and the landed cost of the goods including shipping and duty.

What is left is gross margin before advertising. If that number is not comfortably positive with advertising subtracted at a realistic rate, the product does not work and no amount of optimisation changes it.

Do this per unit and then multiply by the units you can actually sell, not by the units you can afford to buy. Those are different numbers and confusing them is how people end up with capital tied up in stock.

Where the capital goes and why it is stuck

Inventory is cash converted into objects in somebody else's warehouse. It comes back when the goods sell, and if they sell slowly it comes back slowly while accruing storage fees.

That is the risk people underestimate. A product that does not sell is not a break-even outcome; it is a loss that grows monthly and ends with disposal or removal costs.

So the first rule of capital here is to buy a test quantity, prove sell-through, and only then commit. A small unsuccessful order is a cheap lesson; a container is not.

The obligations that come with it

This is a business. That means registering as self-employed or forming a company, VAT registration once turnover crosses the threshold, and product compliance for whatever you sell, safety marking, labelling, and importer obligations if you bring goods in yourself.

Importing makes you responsible for compliance in a way that reselling a domestic brand does not. If you are sourcing from overseas, that responsibility is yours and it is enforced.

Product liability insurance is worth having and is sometimes required. See what the liability covers do and the tax and registration machinery.

Depending on one platform

The structural risk in this business is not competition or fees. It is that the entire operation sits on a single platform that owns the customer relationship, sets the rules, and can suspend an account while it investigates something.

Suspensions happen for reasons that are not always the seller's fault: a complaint about authenticity, a policy interpretation, an automated flag. During one, inventory sits in a warehouse generating storage fees and generating no sales, which is the worst possible combination.

Two mitigations are worth building from the start. Keep the paperwork that proves your supply chain: invoices from the actual manufacturer or authorised distributor, rather than a receipt from a wholesaler, since that is what an authenticity complaint is resolved with. And build any route to customers that you own, however small, so the business is not one account decision away from nothing.

Who this actually works for

Somebody with capital they can afford to lose, a product with a defensible reason to be chosen over the alternatives, and the patience to run the arithmetic before the enthusiasm. It is a real business and real businesses work.

It does not work as a way to make money quickly with little money, which is how it is most often sold. The courses promising that are themselves the business model being described.

See selling without FBA and the routes compared honestly.

Frequently asked questions