For most UK based Amazon FBA businesses, inventory is the single largest asset on the balance sheet, often dwarfing cash and fixed assets combined. HMRC requires stock to be valued at the lower of cost and net realisable value under FRS 102 Section 13, which sounds simple until you factor in inbound freight, customs duty, FBA prep fees and dimensional weight charges that all feed into the true unit cost. Get the valuation wrong and you misstate both the balance sheet and your taxable profit, since HMRC assesses corporation tax on profit calculated after cost of goods sold, not on revenue alone.
What Actually Belongs in Cost of Goods Sold
Cost of goods sold is the direct cost of the units you sold in the accounting period, not everything you spent on the product. For FBA sellers this typically includes the supplier invoice cost, inbound freight to the UK, import duty, and any prep, labelling or inspection fees incurred before the stock became sellable on Amazon. Ongoing FBA fulfilment fees, storage charges and advertising spend are usually treated as operating expenses rather than COGS, though practice varies between accountants, and what matters most is applying the same categorisation consistently year on year so your gross margin actually reflects business reality. Mixing these up understates or inflates gross margin and can distort pricing decisions as well as the figures HMRC sees on your tax return.
| Cost type | Typical treatment |
|---|---|
| Supplier invoice cost | COGS |
| Inbound freight and customs duty | COGS |
| Prep, labelling, FNSKU stickers | COGS |
| FBA storage and fulfilment fees | Operating expense |
| Amazon advertising (PPC) | Operating expense |
| Returns processing fees | Operating expense |
Choosing a Costing Method: FIFO or Weighted Average
UK GAAP under FRS 102 and IFRS both permit First In First Out (FIFO) and Weighted Average Cost (AVCO), while LIFO is explicitly prohibited. FIFO assumes the oldest stock sells first, so cost of goods sold reflects earlier purchase prices, which matters when supplier costs are rising. AVCO recalculates a blended average cost every time new stock arrives and applies that figure to every unit sold in the period, smoothing out price fluctuations. Most product based Amazon sellers in the UK default to one of these two methods, and switching between them without disclosure can trigger questions from HMRC or your accountant during year end review.
Tracking Stock as It Moves Through Amazon’s Network
Stock enters as inbound shipments to Amazon warehouses and leaves through customer sales, returns, removals or disposals, and every one of those movements needs to be captured accurately in your books. Spreadsheet tracking tends to break down once a seller passes a handful of SKUs across multiple fulfilment centres, since Amazon splits inventory across warehouses and reports units without giving you a cost basis. Specialist connectors such as A2X, SellerBoard or Link My Books pull settlement and inventory data directly from Seller Central and post it into Xero or QuickBooks with the correct cost mapping, which keeps monthly management accounts aligned with what actually happened in the warehouse.
Returns, Damaged Stock and Amazon Reimbursements
Not every return is the same, and treating them identically is one of the most common inventory errors we see. Stock that comes back sellable should return to inventory at its original cost. Stock that comes back damaged or unsellable should be written off as an expense in the period it is identified. Units that Amazon loses or damages and later reimburses you for should be recorded as income, separate from sales revenue, once the reimbursement is confirmed. Failing to distinguish between these scenarios understates inventory in one direction and overstates expenses or revenue in another, distorting both gross margin and taxable profit at the same time.
VAT Considerations Specific to FBA Inventory
Holding stock in a UK Amazon warehouse creates a UK VAT registration obligation, and the rules differ depending on where your business is established. UK established sellers register once taxable turnover exceeds £90,000 in a rolling 12 month period, though many register voluntarily earlier to reclaim VAT on stock and software costs. Non established taxable persons storing goods in a UK fulfilment centre have no threshold at all and must register before their first UK sale, typically within 90 days of stock arriving in a UK warehouse or Amazon may suspend the listing.
Since January 2021, Amazon acts as deemed supplier for certain low value or overseas seller transactions, collecting and remitting VAT itself, which means those specific sales must be excluded from your own VAT return calculations to avoid double counting. Import VAT on inbound stock is generally recoverable as input tax once you hold a valid VAT invoice, and all VAT records must be kept under Making Tax Digital compliant software for at least six years.
Year End Stock Valuation: Where Sellers Get Caught Out
At year end you need an accurate count of stock sitting across all Amazon FBA warehouses, valued at cost rather than selling price. Amazon’s reports give you unit quantities but never a cost basis, so you must apply your chosen FIFO or AVCO method to convert those units into a pound figure for the balance sheet. A valuation error of only a few thousand pounds in either direction moves taxable profit by the same amount, and this can shift a corporation tax bill by a four figure sum without anyone noticing until the accounts are already signed off. Reconciling Amazon’s unit counts against your accounting software before the year end close is one of the simplest ways to avoid an unpleasant surprise from HMRC later.
Setting Up Inventory Accounting Correctly From Day One
Getting Amazon inventory accounting right is not a one off task, it is an ongoing discipline that needs to be embedded into your bookkeeping from the first shipment. A specialist ecommerce accountant sets up inventory tracking properly, integrates it with cloud accounting software, applies a consistent costing method, and reviews the figures every month rather than only at year end. The result is that you always know your real gross margin, your real tax exposure and your true stock value, which underpins every pricing, cash flow and growth decision you make as a seller.
How UK Ecommerce Accountants Can Help
Amazon FBA inventory accounting touches product costing, VAT, corporation tax and monthly bookkeeping all at once, and getting any one part wrong ripples through the rest of your accounts. Our team at UK Ecommerce Accountants specialises exclusively in Amazon and multichannel sellers, so we know exactly where the numbers tend to go wrong.
- We set up and reconcile A2X, Link My Books or SellerBoard connectors so your Amazon settlements and inventory movements flow correctly into Xero or QuickBooks
- We choose and consistently apply the right costing method, FIFO or weighted average, tailored to your product mix and pricing pattern
- We separate true cost of goods sold from operating expenses so your gross margin and management accounts reflect reality
- We handle UK VAT registration, quarterly returns and Making Tax Digital compliance for both UK established and overseas sellers holding FBA stock
- We manage returns, damaged stock write offs and Amazon reimbursement income so nothing is double counted or missed
- We perform accurate year end stock valuations across all FBA warehouses to protect you from unexpected corporation tax bills
- We provide monthly management accounts and margin reporting so you always know your real profitability, not just your Amazon payout
Faqs:
Do I need to register for UK VAT if I only use Amazon FBA?
Yes, if your stock is stored in a UK Amazon warehouse, you generally must register for VAT, either at the £90,000 threshold if UK established, or immediately if you are a non established seller.
What costs should be included in cost of goods sold for Amazon FBA?
COGS should include the supplier invoice cost, inbound freight, customs duty and any prep or labelling costs incurred before the product becomes sellable, while ongoing FBA fees and advertising are usually treated as operating expenses.
Should I use FIFO or weighted average cost for my Amazon stock?
Both are accepted under UK GAAP, FIFO suits sellers with rising supplier costs, while weighted average suits sellers who want smoother, more stable cost figures across the year.
How do Amazon returns affect my inventory accounting?
Sellable returns go back into inventory at cost, damaged stock is written off as an expense, and any Amazon reimbursement for lost or damaged stock is recorded as separate income.
Why does my year end stock valuation matter for tax?
An incorrect stock valuation directly changes your taxable profit for the year, which can move your corporation tax liability by a significant amount even from a small valuation error.
Can accounting software calculate my FBA inventory automatically?
Tools like A2X, Link My Books and SellerBoard can pull Amazon data automatically, but you still need an accountant to apply the correct costing method and categorisation for accurate results.
