How to fill in the SA103 self-employment pages
If you are trading and over the £1,000 allowance, your reselling goes on the SA103 self-employment pages of your Self Assessment return. It looks official, but for a reseller only a handful of boxes matter. Here is what each one means.
General information, not tax advice. Check with HMRC or a qualified accountant before you act on it.
SA103S or SA103F: which one
Most resellers use the short version, SA103S. The full SA103F is for larger or more complex businesses. If your turnover is under £90,000, the short pages are almost certainly the ones for you.
Your turnover: total sales
This box is your total sales for the tax year, before any fees or costs come off. It is the full amount buyers paid you, added up across every platform. Not your payout, and not your profit: the gross sales figure.
Allowable expenses: your costs
Here you put the costs of running your reselling: platform fees, postage, packaging, and what you paid for the stock you sold. You can either total these up, or claim the flat £1,000 trading allowance instead, whichever is higher. You cannot do both.
Net profit: the number tax is based on
Turnover minus your allowable expenses gives your net profit. This is the figure your Income Tax and Class 4 National Insurance are worked out on. Get your sales and costs right and this box takes care of itself.
Where FlipTally fits
The tedious part is adding up sales, fees and postage across a whole year of orders. Connecting your eBay account pulls those in automatically, and FlipTally produces an SA103-style summary with the turnover, expenses and profit figures already totalled, so you can copy them straight across.
Frequently asked questions
What is the SA103?
It is the self-employment section of the Self Assessment tax return, where you declare your reselling turnover, expenses and profit. Most resellers use the short version, SA103S.
Do I put my sales or my profit as turnover?
Turnover is your total sales before costs, the full amount buyers paid. Your profit comes after you subtract allowable expenses further down the form.
Can I claim the £1,000 allowance on the SA103?
Yes. Instead of listing real expenses you can claim the flat £1,000 trading allowance, whichever gives you the lower profit. You choose one or the other, not both.
See where you actually stand
Get a rough answer in about a minute with the free calculator, or connect your eBay account to see your real profit and tax.
Related guides
This guide is general information, not tax advice, and reflects the UK rules for the current tax year. Always check with a qualified accountant before you file. FlipTally is independent and not affiliated with, endorsed by or connected to eBay, Vinted, Depop or HMRC. Last updated 2026-08-04.