File your Self Assessment tax return

A Self Assessment return reports your income and gains for a tax year, which runs from 6 April to 5 April. HMRC uses it to work out your Income Tax, your Class 4 National Insurance contributions if you are self-employed, and any Capital Gains Tax. You can send the return at any time after the tax year ends, and sending it early shows you what you owe and gives you time to arrange payment.

Check that you need to file

You must send a return if you were a self-employed sole trader and earned more than £1,000 before taking off anything you can claim tax relief on. You must also send one if you were a partner in a business partnership, had to pay Capital Gains Tax on a disposal, or had to pay the High Income Child Benefit Charge and do not pay it through PAYE. A return is also needed if you have untaxed income, such as rental income, tips and commission, savings interest, dividends or foreign income. You must send a return whenever HMRC asks you to.

Register with HMRC

If you have not filed before, or you registered before but did not need to file for the previous tax year, tell HMRC by 5 October after the end of the tax year. For example, for the 2025 to 2026 tax year, register by 5 October 2026. If you register late and still owe tax after 31 January, HMRC can charge a failure to notify penalty based on the tax left unpaid. If you registered in the past, you may need to reactivate your Self Assessment account, and filing before you do can delay your return. Once HMRC has sent your Unique Taxpayer Reference (UTR) and you have activated your online account, you can file online.

Know the deadlines

Have your records ready

You need records that support every figure on the return. Have these in front of you before you start:

• Your UTR and National Insurance number.
• Records of your business income and expenses for the tax year, such as invoices, bank statements and receipts.
• Your P60 or P45, if you also had employment.
• Bank interest statements and dividend vouchers.
• Records of pension contributions and charitable donations, if you are claiming relief.
• Records of any assets you bought or sold, if you have gains to report.

If you do not know your profit for the whole tax year when you file, for example because your accounting period ends on a different date, send provisional figures and tell HMRC that you have. Change the return when you know the final figures, within 12 months of the filing deadline. If more tax is due, you pay interest on the difference from the original due date.

Send the return

Most people file online through their HMRC account. If you need paper, call HMRC or download the SA100 form, and make sure HMRC receives it by the paper deadline. Some returns, such as those for partnerships, trusts and non-residents, can be filed with commercial software. The online service asks about your circumstances and picks the pages you need, including the self-employment pages.

Pay what you owe

Understand payments on account

Payments on account are advance payments towards next year's bill, including Class 4 National Insurance contributions if you are self-employed.

If you have not made payments on account before, you pay the whole bill and the first payment on account together on 31 January, which is half as much again as the bill itself. If you expect lower income, you can ask HMRC to reduce your payments on account online or on form SA303. If you reduce them too far and your bill turns out higher, you pay interest on the difference. If you cannot pay in full by the deadline, contact HMRC before it to arrange a payment plan.

Know the penalties for paying late

If you file late, penalties apply even when you owe no tax.

If you have a reasonable excuse, you can appeal a penalty.

Correct a mistake after you file

You can correct a return online or by sending corrected pages marked "amendment". Wait 3 days after filing before you update an online return.

Keep your records

Check whether Making Tax Digital applies

Making Tax Digital for Income Tax is replacing the traditional return for sole traders and landlords whose qualifying income is above a threshold. If it applies to you, you keep digital records in compatible software and send updates during the year. HMRC writes to you if your qualifying income is over the threshold, but you are responsible for checking whether it applies, even without a letter. You must still file a Self Assessment return for the tax year before you start.