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UK tax return builder: your Self Assessment, box by box

Enter your real figures once. Every one lands on its actual HMRC box across SA102, SA103S, SA105, the SA101 additional information schedule and SA100, with the official GOV.UK page beside it and an SA302 style calculation at the end.

Nothing entered yet, so nothing is owed

You have not put any income in on the left, so every box below is nought. We never fill in a wage, a profit or a rent for you.

2025/26 Self Assessment estimate

Your SA100 summary

Total income

£0

Business and rental costs

0

Pension and other reliefs

0

Before allowances

£0

Estimated tax and National Insurance

£0

After lawful planning

£0

You could keep

£320

Your filled return, form by form

In filing order, because each set of pages feeds the SA100. Anything showing a dash is a figure only you hold, such as tax already taken off by your employer.

SA101

Additional information (the UK's Schedule 1)

31 January online, 31 October on paper

The extra schedule that goes with SA100 for anything the main pages have no room for: savings and investment income, share schemes, investment reliefs and pension charges. These are figures only you hold, so we show you the exact box each one belongs in.

BoxWhat goes in itAmount
Page Ai1 box 1Interest from gilt-edged and other UK securities, deeply discounted securities and accrued income profits
Page Ai1 box 3Gains from life insurance policies, capital redemption policies and life annuity contracts
Page Ai1 box 12Taxable amount from share schemes not already on your P60
Page Ai2 box 1Subscriptions for Venture Capital Trust shares

30 per cent income tax relief on up to 200,000 pounds a year.

Page Ai2 box 2Subscriptions for shares under the Enterprise Investment Scheme

30 per cent income tax relief, and the shares can be free of Capital Gains Tax.

Page Ai2 box 3Subscriptions for shares under the Seed Enterprise Investment Scheme

50 per cent income tax relief on up to 200,000 pounds a year.

Page Ai2 box 8Payments to trade unions or police organisations for death benefits
Page Ai3 box 1Pension savings tax charges, where you went over the annual allowance

The annual allowance is 60,000 pounds, tapered for very high earners.

Page Ai4 box 1Any other information you want HMRC to have
Official GOV.UK page for SA101

SA100

Main tax return

31 January online, 31 October on paper

The front pages that tie the supplementary pages together.

BoxWhat goes in itAmount
Page TR1Your name, address, Unique Taxpayer Reference and National Insurance number
Page TR2 box 1Tick yes if you were self-employed and are sending SA103 pages
Page TR2 box 4Tick yes if you had UK property income and are sending SA105 pages
Page TR4 box 1Payments to registered pension schemes where basic rate relief will be claimed£0
Page TR4 box 3Payments to a retirement annuity contract, where no relief is given at source
Page TR5 box 1Gift Aid payments made in the year
Page TR8Sign, date and keep a copy with your records for at least five years
Official GOV.UK page for SA100

SA302 tax calculation

What the return works out to

Tax and the first payment on account are due by 31 January

HMRC produces this calculation from the boxes above. Compare it to these figures before you accept it.

BoxWhat goes in itAmount
Line 1Income tax£0
Official GOV.UK page for SA302 tax calculation

Before you file

This is an estimate built from what you typed, using HMRC figures for the current tax year. It is here so you can check an accountant's work, see where every number belongs and plan lawfully. It is not a filed return, and it does not replace personal advice.

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