You need to value your stock at the lower of cost or what you could reasonably sell it for, and — critically — unsold stock at your year end isn't a deductible expense; only the cost of goods you've actually sold during the year reduces your taxable profit.
This trips up a lot of new e-commerce sellers who buy a large batch of stock, expense the whole purchase immediately, and then find their tax bill doesn't match their cash position because half of it is still sitting unsold in a garage. Getting a proper cost-of-goods-sold figure means tracking what you bought, what you sold, and what's left, not just totalling up supplier invoices. If you're selling across Amazon, Etsy, Shopify or eBay at once, this gets more complicated fast, since stock might be held in different places (your own storage vs. Amazon FBA warehouses) with different costs and timing. If you've been expensing stock purchases as you buy them rather than as you sell them, your reported profit is probably wrong — worth getting this corrected before your next return, not after HMRC queries it.
We set up proper cost-of-goods-sold tracking for online sellers, so your reported profit actually matches your stock position.
Talk to an AccountantYou need to value your stock at the lower of cost or what you could reasonably sell it for, and — critically — unsold stock at your year end isn't a deductible expense; only the cost of goods you've actually sold during the year reduces your taxable profit.