A-to-z Guarantee

Amazon's buyer protection. A claim usually costs you the sale and counts against your order defect rate, and on FBM orders you carry the loss rather than Amazon.

ACoS

Advertising cost of sale: ad spend divided by the sales those ads produced. Amazon reports it by default, which is why sellers here think in ACoS while everyone else thinks in ROAS. The two are reciprocals of each other.

Aged Inventory Surcharge

An extra monthly storage charge on stock held past a threshold, 241 days in the UK. It climbs at each later tier. American articles say 181 days, which is a different marketplace.

Amazon Warehousing and Distribution

Bulk storage upstream of the fulfilment centres, priced lower per cubic foot and used to feed FBA. Stock there is still yours and still counts at your year end.

ASIN

Amazon Standard Identification Number, the ten-character code for a product on the catalogue. One ASIN can carry several sellers, which is why margins have to be tracked per ASIN rather than per listing.

Best Sellers Rank

A relative sales ranking within a category, updated hourly. Useful for gauging demand and useless as a business metric, because it says nothing about price, margin or volume.

Brand Registry

Enrolment that gives a trademark owner control over their listings and access to extra advertising formats. Not an accounting matter, but the trademark cost is a deductible intangible.

Buy Box

The featured offer, and the source of most sales on a shared listing. Winning it depends on price, fulfilment method and seller metrics, and losing it can halve revenue overnight without anything changing in your accounts.

Capacity Limits

A cap on how much stock you may send in, set by your Inventory Performance Index. Hitting it in the fourth quarter is the reason restock planning has to happen in the third.

Central Europe Programme

A middle option between one country and full Pan-EU: stock is placed in Poland and Czechia as well as Germany. It creates VAT registration obligations in those countries just as Pan-EU does.

Commingled Inventory

Stock pooled with other sellers' identical units rather than labelled to you. It speeds up fulfilment and makes reimbursement claims harder to evidence, because the unit shipped was not necessarily yours.

Deemed Supplier

The rule making Amazon rather than you responsible for VAT on certain sales. It removes the output tax and leaves your registration and filing obligations exactly where they were.

Digital Services Fee

A percentage charged on your Amazon fees rather than on the sale, currently 2 per cent for UK sellers. Small, easy to forget, and on every single order.

Disbursement

The transfer of a settlement to your bank. It is the net of a fortnight of sales and every deduction, so it is not turnover and should never be booked as such.

Disposal Order

An instruction to destroy stock rather than return it. Cheaper than a removal, and the write-off reduces your taxable profit in the period you dispose of it.

EFN

European Fulfilment Network: stock stays in one country and ships cross-border from there. Higher fulfilment fees per unit, one VAT registration instead of five, and usually the right answer below about three hundred EU units a month.

Estimated Fee Preview

Amazon's forecast of the referral and fulfilment fees on a listing. A forecast, not a bill: size tier remeasurements routinely move the real figure.

FBA

Fulfilment by Amazon. Amazon stores, picks, packs and ships, and handles most returns. The stock is still yours, wherever it sits, and still counts in your year-end count.

FBM

Fulfilment by Merchant. You ship it yourself. Cheaper per unit on paper and rarely cheaper once your own time is costed at anything above a couple of pounds an hour.

Fiscal Representative

A local agent jointly liable for your VAT, required in several EU countries for businesses established outside the EU. They charge for it, and they usually want a deposit or guarantee first.

FNSKU

The barcode Amazon uses to identify your specific units in the fulfilment network. Labelling with it is what keeps your stock out of the commingled pool.

Fulfilment Fee

The per-unit charge for picking, packing and shipping an FBA order, set by size tier. A variable cost, so it belongs in contribution rather than overheads.

Gated Category

A category needing approval before you can list in it. The approval cost, including any sample purchases, is deductible.

Inbound Shipment

Stock sent into the fulfilment network. The commonest reimbursement claim starts here, when fewer units are checked in than you sent, and the packing list is your evidence.

Inventory Ledger

The report showing every movement of your stock: received, sold, lost, damaged, disposed, transferred. The starting point for both a stock count and a reimbursement claim.

Inventory Performance Index

A score covering sell-through, stranded stock, excess stock and in-stock rate. It sets your capacity limits, so it is a cash flow constraint rather than a vanity metric.

IOSS

Import One Stop Shop, for consignments up to 150 euros sent into the EU from outside it. From 1 July 2026 a flat three euro customs charge applies to these consignments anyway, including ones reported through IOSS.

Long-Term Storage Fee

The older name for what is now charged as an aged inventory surcharge. Same idea: stock that will not sell costs more the longer it does not.

Low-Inventory-Level Fee

A charge applied when your stock cover runs persistently thin relative to sales. It penalises the opposite behaviour to the aged surcharge, which is why restocking is a range rather than a target.

Marketplace Facilitator

The rules making a marketplace responsible for collecting tax on sales it facilitates. It is why Amazon often collects the VAT and why sellers wrongly conclude they no longer need to register.

Monthly Storage Fee

Charged per cubic foot on the daily average volume your stock occupies, and considerably higher in the fourth quarter. Measured on the packed unit, not the product.

Multi-Channel Fulfilment

Using FBA stock to fulfil orders from your own website or another marketplace. The fee is higher than a normal FBA fee and the sale is not an Amazon sale, which matters for how you record it.

Order Defect Rate

The share of orders with a negative feedback, an A-to-z claim or a chargeback. Above the threshold it puts the account at risk, which makes it a business risk rather than a service metric.

Oversize

A size tier above standard, with its own fulfilment and storage rates. A centimetre can move a product between tiers and change its economics entirely.

Pan-EU FBA

The programme that distributes your stock across five or more EU countries. Holding stock in a country requires VAT registration there, from day one and at any volume, so one setting creates five foreign registrations.

Placement Fee

A charge for sending stock to fewer fulfilment centres than Amazon would prefer. Splitting a shipment avoids it and costs you freight, so it is a trade rather than a saving.

Prep

Polybagging, labelling, bundling and anything else required before stock can be received. A per-unit variable cost, whether you do it or pay someone.

Professional Selling Plan

The monthly subscription for a seller account, currently £25 plus VAT. A fixed overhead rather than a cost of sale, so it belongs below contribution.

Referral Fee

Amazon's commission on a sale, usually 15 per cent, charged on the full price the buyer paid including VAT and with a 25p minimum. Being charged on the gross price is why VAT registration cuts your advertising headroom so sharply.

Reimbursement

Money Amazon repays for units it lost, damaged, disposed of without instruction, or refunded without receiving a return. Claims expire, so the log matters more than the filing.

Removal Order

An instruction to send stock back to you rather than destroy it. Worth doing before an aged surcharge tier rather than after, and the cost is deductible.

Reserve

Money held back by Amazon against future refunds and chargebacks. It is still your money and sits on your balance sheet as an asset, not as a cost.

Restock Limits

The cap on units you may send in, derived from your Inventory Performance Index. Plan around it in the third quarter or discover it in the fourth.

Returnless Refund

A refund issued without asking for the item back, usually where return shipping exceeds the value. You lose the unit and the sale, which makes it the most expensive kind of return.

Seller Central

The seller-facing console. Every figure in this glossary comes out of it somewhere, and several of its reports are only downloadable for a limited window.

Settlement

The fortnightly batch in which Amazon nets the transactions it has collected against every fee, refund and reserve movement, then pays over the remainder. Half your weeks therefore have no income in them at all.

Settlement Report

The itemised statement behind a disbursement. It is the only document that bridges gross sales to the money that arrived, and without it the gap cannot be explained.

Size Tier

The band a product falls into by dimensions and weight, which sets both the fulfilment fee and the storage rate. Amazon remeasures, and a wrong tier is a reclaimable overcharge.

Sponsored Products

Amazon's main pay-per-click format. Judge it against your break-even ACoS rather than against a round number, because the number that works differs by product.

Stranded Inventory

Stock in a fulfilment centre with no active listing attached. It cannot sell, it still accrues storage, and it still ages towards the surcharge.

Subscribe and Save

A recurring-order programme with a funded discount. The discount is a reduction in revenue rather than a marketing cost, which matters for both margin and turnover.

TACoS

Total advertising cost of sale: ad spend against all sales, organic included, rather than only attributed ones. More forgiving than ACoS and a better measure of whether advertising is building anything.

Transaction Report

The order-level detail behind a settlement. Where you go when the summary does not reconcile, and one of the reports with a short download window.

Unfulfillable Inventory

Stock Amazon will not ship: damaged, expired, or in a category you have lost approval for. It has to be removed or disposed of, and it accrues storage until it is.

VAT Calculation Service

Amazon's optional service for producing VAT invoices and applying rates. Useful, and not a substitute for being registered where your stock is.

Vendor Central

The wholesale relationship, where Amazon buys from you and resells. Entirely different accounting from Seller Central: you are invoicing one customer on terms rather than making thousands of retail sales.