Self Assessment prep workbook
For sole traders getting ready to file their tax return
Get ready for your Self Assessment in one place. Tick off what you need to gather, type in your year's figures, and see an estimate of the Income Tax and Class 4 National Insurance on your profit, worked out band by band so you can follow it. It also shows whether payments on account are likely and what falls due on the 31 January and 31 July after the tax year.
Inside the workbook
- ChecklistWhat to gather before you start
- Your figuresYour year's income, costs and other pay
- EstimateIncome Tax, Class 4 and what's due when
- SourcesEvery rate and rule used, for both tax years, with its GOV.UK link
- Start, How to useA cover with the contents, and plain instructions
Where the figures come from
- Tax year starts
- Tax year ends
- Personal Allowance (standard)
- Allowance cut £1 per £2 of income over
- Basic rate band ends at (income)
- Additional rate on taxable income over
- Basic rate (England, Wales and NI)
- Higher rate of Income Tax
- Additional rate of Income Tax
- Class 4 on profits over
- Class 4 main rate up to profits of
- Class 4 main rate
- Class 4 rate above that
- Trading allowance (instead of costs)
- Class 2 treated as paid from profits of
- No payments on account if bill under
- …or if more than this was paid another way
- Each payment on account: share of the bill
- Return and January payment due
- July payment on account due
A spreadsheet for organising your own figures. It isn't tax advice, isn't HMRC software and can't send anything to HMRC. Check every figure. Rates and thresholds are for the 2025–26 and 2026–27 tax years (you choose which on the Start sheet) and link to GOV.UK, checked on 18 Oct 2026. If you're not sure what applies to you, ask HMRC or an accountant. Sources and dates are on the Sources tab. Contains public sector information licensed under the Open Government Licence v3.0. Not affiliated with or endorsed by HMRC.