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Self Assessment: tax return (SA100)
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SA100 in short
The SA100 is the main paper Self Assessment tax return. It is used to report taxable income and gains and to claim tax reliefs for the tax year 6 April 2025 to 5 April 2026. Most people file online instead, which gives an extra 3 months to send the return.
| Issued by | HM Revenue and Customs (HMRC) |
|---|---|
| Current version | SA100 2026 (HMRC 12/25) (checked 2026-10-25) |
| Who fills it in | People who must send a Self Assessment tax return, for example sole traders who earned more than £1,000, partners in a business partnership, people with Capital Gains Tax to pay, and people who must pay the High Income Child Benefit Charge and do not pay it through PAYE. You must also send a return if HMRC asks you to. |
| Who receives it | HM Revenue and Customs (HMRC). |
| Where to send it | Use the office address on your most recent letter from HMRC. If you have none and live in the UK, gov.uk says to send it to: Self Assessment, HM Revenue and Customs, BX9 1AS, United Kingdom. If you live outside the UK: HM Revenue and Customs, Benton Park View, Newcastle Upon Tyne, NE98 1ZZ, United Kingdom. You can also file online at www.gov.uk/log-in-file-self-assessment-tax-return. |
| Deadline | For the 2025 to 2026 tax year, gov.uk says HMRC must receive a paper return by 11:59pm on 31 October 2026. An online return must be submitted by 11:59pm on 31 January 2027. Any tax owed must be paid by 11:59pm on 31 January 2027. If HMRC's notice to file was issued late, the deadline is 3 months after the date of the notice if that is later. |
| Official links | Official page · Official PDF · Official instructions |
What changed
The 2026 form covers the tax year 6 April 2025 to 5 April 2026. Page TR 5 has a section for the Winter Fuel Payment and Pension Age Winter Heating Payment charge, for people over State Pension age with total income over £35,000 who are not getting a qualifying benefit. Supplementary question 8 is now titled 'Residence and foreign income and gains (FIG) regime etc'.
How to fill out SA100, line by line
| Page TR 1, boxes 1 to 4 | Your personal details Enter your date of birth, phone number and National Insurance number. If the name and address printed on the front are wrong, write the correct details underneath. |
| Information sheet | UTR, National Insurance number and employer reference Add your 10-digit Unique Taxpayer Reference (UTR), National Insurance number and employer reference if you have one before printing. HMRC says it may send the return back if these are missing. |
| Page TR 2, questions 1 to 9 | What makes up your tax return Answer Yes or No for employment, self-employment, partnership, UK property, foreign income, trusts, capital gains, residence and additional information. Each Yes usually means you also need a separate supplementary page, such as SA102 for employment. |
| Page TR 3, boxes 1 to 7 | Interest and dividends Enter UK interest, untaxed foreign interest up to £2,000, dividends from UK companies and foreign dividends up to £500. Use whole pounds. |
| Page TR 3, boxes 8 to 16 | UK pensions, annuities and state benefits Enter the State Pension you were entitled to for the year, not the weekly or 4-weekly amount. Add other pensions, taxable benefits and any tax taken off. |
| Page TR 4 | Tax reliefs Enter pension contributions not already relieved through your pay, Gift Aid donations, gifts of shares or land to charity and Blind Person's Allowance. |
| Page TR 5 | Student Loan, High Income Child Benefit Charge, Marriage Allowance, Winter Fuel Payment charge Fill in only the sections that apply. For the High Income Child Benefit Charge, enter the total Child Benefit received and the number of children if your income was over £60,000 and higher than your partner's. |
| Page TR 6, boxes 1 to 3 | Tax refunded and paying through your tax code Enter any 2025 to 2026 tax already refunded. Put X in box 2 if you do not want HMRC to collect an amount under £3,000 through your tax code. |
| Page TR 6, boxes 4 to 14 | Repayment bank details If you have paid too much tax, give the bank or building society name, account holder, sort code and account number. A nominee needs your signature in box 14. |
| Page TR 7 | Tax adviser and any other information Optional details of your tax adviser. Use box 19 to explain anything, such as provisional figures. |
| Page TR 8, boxes 20 to 26 | Declaration Mark if figures are provisional or if you are enclosing supplementary pages, then sign and date box 22. If signing for someone else, fill in boxes 23 to 26. |
Common mistakes to avoid
- Sending the paper return after 31 October 2026. If you miss the paper deadline, gov.uk says to file online instead to avoid a penalty.
- Leaving out the UTR or National Insurance number on the information sheet, which can mean HMRC sends the return back.
- Forgetting the supplementary pages (for example SA102 or SA103S) when you answered Yes on page TR 2.
- Entering pence. The form asks for whole pounds, rounding income down and expenses and tax paid up.
- Striking through or writing in empty boxes. The form says to leave boxes that do not apply blank.
- Not signing and dating the declaration at box 22 on page TR 8.
- Entering payments on account or other payments already made. HMRC deducts these on your Self Assessment statement instead.
Questions about SA100
When is the paper SA100 due for the 2025 to 2026 tax year?
gov.uk says HMRC must receive a paper return by 11:59pm on 31 October 2026. The online deadline is 11:59pm on 31 January 2027.
Can I file online instead of using the paper form?
Yes. You can file at www.gov.uk/log-in-file-self-assessment-tax-return. HMRC says online filing gives you an extra 3 months and you can save and finish later.
What is the penalty for a late return?
gov.uk lists an initial £100 penalty, then £10 a day after 3 months up to £900, and further penalties after 6 and 12 months. Interest and late payment penalties apply to tax paid late.
Do I need to register before sending a return?
If you have not sent a return before, gov.uk says you must tell HMRC by 5 October after the end of the tax year by registering for Self Assessment.
Do I have to work out my own tax?
No. If HMRC receives the paper return by 31 October 2026, or you file online, HMRC will do the calculation for you. You can ask for the 'Tax calculation summary' pages if you want to work it out yourself.
Can I correct my return after sending it?
Yes. gov.uk says you can correct a return within 12 months of the Self Assessment deadline, online or by sending another paper return.
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Sources
Checked against the official sources on 2026-10-25. PDF Editor Hub is not affiliated with the HM Revenue and Customs or any government agency. This page is general information, not legal or tax advice.
- https://www.gov.uk/guidance/how-to-complete-your-self-assessment-tax-return-for-last-tax-year
- https://www.gov.uk/self-assessment-tax-returns
- https://www.gov.uk/self-assessment-tax-returns/deadlines
- https://www.gov.uk/self-assessment-tax-returns/penalties
- https://assets.publishing.service.gov.uk/media/69c14d07cfa346b9d4704a8d/SA100-2026.pdf
- https://assets.publishing.service.gov.uk/media/6a9ea8a5df4246cf45e469e0/SA150_Notes_2026.pdf