Guides / Self-employment (short)

The Self-employment (short) pages, box by box

Tax year 2025-26. Checked against HMRC's SA103S 2026 form and GOV.UK rates, October 2026.

If you have a side business or do some self-employed work alongside your job, you'll probably use the short pages (SA103S). This guide covers what goes in each box, when the £1,000 trading allowance helps, and how National Insurance works.

Can you use the short pages?

Use them if your business turnover was under £90,000 for the year (the VAT threshold) and your affairs are simple.
If turnover was £90,000 or more, or you need more detail (for example some capital allowance or basis-period adjustments), use the full pages (SA103F).
If your total trading income (before costs) was £1,000 or less, the trading allowance covers it and you don't need to report it.

The main boxes

Box	What it asks	Notes
1	Description of business	A few words, e.g. "Dog walking".
9	Your turnover	All money earned from the business in the year, before costs.
10	Any other business income	For example grants or insurance payouts. Not turnover.
10.1	Trading income allowance	Up to £1,000, instead of claiming expenses.
11-19	Expenses by type	Optional when turnover is under £90,000. You can just put the total in box 20.
20	Total allowable expenses	All business costs.
21 / 22	Net profit / net loss	Boxes 9 + 10 minus box 20.
23	Annual Investment Allowance	Equipment bought for the business, such as tools, computers or a van. Not cars.
27	Goods or services for your own use	Stock you took for yourself.
28	Net business profit for tax purposes	Profit after capital allowances and adjustments.
29	Losses brought forward used this year	Unused trading losses from earlier years.
31	Total taxable profits from this business	The figure you're taxed on.
36	Voluntary Class 2 NICs	Only if profits are under £6,845 and you want to pay voluntarily.
38	CIS deductions	Tax already taken by contractors (construction only).

Trading allowance or expenses?

You can take £1,000 off your income (box 10.1) or claim your actual costs, but not both. Pick whichever is bigger. If you use the allowance, you can't claim capital allowances either.

Example

Chris walks dogs alongside a full-time job. Turnover was £8,000 and costs (insurance, leads, a share of the car at 45p a mile) came to £1,500.

	Allowance	Actual costs
Box 9 turnover	£8,000	£8,000
Box 10.1 / box 20	£1,000	£1,500
Box 31 taxable profit	£7,000	£6,500

Actual costs win by £500 of profit, which is £100 less tax for a basic-rate taxpayer. Profit is under £12,570, so there's no Class 4 National Insurance.

National Insurance for 2025-26

Class 4: 6% on profits between £12,570 and £50,270, and 2% above that. This is on top of employee NI from your job.
Class 2: no longer compulsory. If profits are £6,845 or more, you get the National Insurance credit automatically. Below that you can pay voluntarily (£3.50 a week, £182 for the year) to protect your State Pension record. If your job already gives you a qualifying year, you usually don't need to.

Example: profits of £30,000 mean Class 4 of (£30,000 - £12,570) x 6% = £1,045.80.

Get your own figures. Enter your turnover and costs. The calculator compares the trading allowance with your actual costs, works out tax and NI on top of your job, and lists each box to enter.

Work out my figures - free

Sources

General guidance, not tax advice.