Stock Valuation Methods for UK Businesses: FIFO, AVCO, and More

Why stock valuation matters

Your unsold stock at year-end sits on your balance sheet as a current asset. The cost assigned to that stock directly affects two things:

• Your profit: Cost of Goods Sold (COGS) is calculated as opening stock + purchases − closing stock. A higher closing stock value = lower COGS = higher gross profit. A lower closing stock value = higher COGS = lower gross profit.
• Your tax bill: Lower profit means lower Corporation Tax (currently 19–25% in the UK depending on your profit level).

In a single accounting period, the method you use can shift tens of thousands of pounds between your reported profit and the value sitting on your balance sheet. Over multiple years, the total profit is the same — it just falls in different periods. But timing matters, especially for managing cash flow and tax payments.

UK rules: what's allowed

UK stock valuation is governed by:

• FRS 102 (the main UK GAAP standard for small and medium businesses) — requires stock to be valued at the lower of cost and net realisable value (NRV). Allows FIFO or weighted average cost. Prohibits LIFO.
• IFRS (used by listed companies and some subsidiaries) — same positions: FIFO or weighted average allowed; LIFO prohibited.
• HMRC guidance — follows the accounting standards. LIFO is not accepted for tax purposes. FIFO and AVCO are both acceptable.

LIFO (Last In, First Out) is not legal in the UK.It is permitted in the US under US GAAP but specifically prohibited under IFRS and UK GAAP. If you've encountered LIFO in an American accounting textbook or software, be aware it does not apply to your UK business.

FIFO explained with an example

FIFO (First In, First Out) assumes that the oldest units you purchased are the first ones you sell. This mirrors physical reality for most products — you clear older stock before newer stock arrives.

Example: You sell a single product. Your purchase history:

• January: buy 100 units at £10 each (£1,000 total)
• March: buy 100 units at £12 each (£1,200 total)

Total stock: 200 units at total cost £2,200. Average cost = £11 per unit.

You sell 120 units during the year. Under FIFO:

• COGS: 100 units × £10 + 20 units × £12 = £1,240
• Closing stock: 80 units × £12 = £960

The closing stock reflects the cost of the most recently purchased units. In a rising cost environment (supplier prices going up), FIFO produces a higher closing stock value and a lower COGS — meaning higher reported profit and a higher tax bill in the short term.

Weighted average cost (AVCO)

Weighted average cost (AVCO) calculates a single blended cost per unit across all units in stock. Every time you receive new stock, the average cost is recalculated.

Using the same example: After January purchase, cost per unit = £10.00. After March purchase:

• Total cost = £1,000 + £1,200 = £2,200
• Total units = 200
• New average cost = £2,200 ÷ 200 = £11.00 per unit

You sell 120 units:

• COGS: 120 × £11.00 = £1,320
• Closing stock: 80 × £11.00 = £880

AVCO produces a COGS of £1,320 versus FIFO's £1,240 in a rising cost environment — meaning lower reported profit and a slightly lower tax bill. The difference smooths out over time, but timing of recognition varies.

AVCO is typically the simpler method to implement because you don't need to track the exact cost of each batch of stock separately — you just maintain one running average per SKU.

Specific identification

Specific identification tracks the actual cost of each individual unit. When unit #5 sells, you record its exact cost as COGS.

This is only practical for products where individual units can be uniquely identified — typically high-value items like vehicles, bespoke jewellery, fine art, or serialised electronics. It's not viable for commodity products where units are interchangeable.

For ecommerce sellers, specific identification is rarely used. The tracking overhead is prohibitive for most product categories, and FIFO or AVCO are perfectly adequate.

The lower of cost and NRV rule

Regardless of which cost method you use, UK GAAP requires stock to be stated at the lower of cost and net realisable value (NRV).

NRV is the estimated selling price minus any costs necessary to make the sale (e.g., refurbishment costs, selling fees, disposal costs).

This rule applies to each product line separately — you can't offset one product's write-down against another product's excess value.

Practical examples:

• You have 50 units of a product that cost you £20 each but is now selling for £15 on eBay. NRV = £15 − £2 (eBay fees) = £13. You must write the stock down to £13 per unit: write-down of (£20 − £13) × 50 = £350.
• You have end-of-season stock that cost £30 but will only sell in January for £25 in a clearance sale. Write it down to £25 at year-end.
• Stock that is damaged beyond sale should be written down to £0 (or scrap value).

Stock write-downs are a recognised expense that reduces your taxable profit. They also ensure your balance sheet accurately reflects the value you'll actually recover from the stock — rather than showing an inflated asset value.

Which method should you use?

For most UK ecommerce small businesses, weighted average cost (AVCO) is the most practical choice. It's simpler to implement, smooths out price fluctuations, and is fully accepted by both FRS 102 and HMRC. Most inventory software can calculate AVCO automatically.

Choose FIFO if:

• You sell perishable goods, trend-sensitive items, or anything with an expiry date — in these cases, you physically must sell older stock first, so FIFO reflects reality
• Your supplier prices are rising significantly and you want your COGS to reflect the actual cost sequence (though this typically means higher short-term profit and tax)
• Your accountant or the nature of your business makes FIFO the cleaner choice

The method you choose must be applied consistently.You can't switch between FIFO and AVCO year to year to get the most favourable outcome in each period — that would be a change in accounting policy and requires disclosure and restating prior periods under FRS 102.

If you're unsure which method to use, speak to your accountant before your first year-end. The choice is easy to make correctly at the start and expensive to unwind later.

Frequently asked questions

Is LIFO allowed in the UK?

No. LIFO is prohibited under both FRS 102 and IFRS as applied in the UK. HMRC also does not accept it for tax purposes. UK businesses must use FIFO or AVCO.

Which stock valuation method is best for a small ecommerce business?

For most UK ecommerce businesses selling identical units, weighted average cost (AVCO) is the most practical. It smooths price fluctuations and doesn't require tracking costs by batch. FIFO suits businesses where older stock genuinely sells first, such as perishable goods or fashion.

How does stock valuation affect my tax bill?

Stock valuation affects your COGS, which reduces your taxable profit. In a rising cost environment, FIFO produces lower COGS (and higher profit/tax); AVCO is somewhere in between. The long-run total tax is similar under both methods — the difference is in timing.

Do I need to value all my stock for year-end accounts?

Yes. UK limited companies must value stock at the lower of cost and net realisable value at year-end. Damaged, obsolete, or slow-moving stock that would sell for less than cost must be written down to expected selling price minus selling costs. These write-downs are a tax-deductible expense.