When do I register for Self Assessment and file my first UK tax return?

Checked on 2026-10-25

If you need a tax return and have never sent one, tell HMRC by registering for Self Assessment by 5 October after the tax year ends. For 2025-26, the paper return is due by 31 October 2026, the online return and payment by 31 January 2027. Late returns start at a £100 penalty.

Key facts

What	The guidance says (2025-26 tax year)	Source
Tell HMRC you need a return	By 5 October 2026, if you have not sent a return before	GOV.UK, Check how to register for Self Assessment; Self Assessment tax returns, deadlines
Paper return	HMRC must receive it by 11:59pm on 31 October 2026	GOV.UK, Self Assessment tax returns, deadlines
Online return	By 11:59pm on 31 January 2027	GOV.UK, Self Assessment tax returns, deadlines
Pay the tax	By 11:59pm on 31 January 2027; a second deadline of 31 July applies to payments on account	GOV.UK, Self Assessment tax returns, deadlines
Registered after 5 October 2026	Filing deadline is 3 months from the date on HMRC’s letter or email; payment is still due by 31 January 2027	GOV.UK, Self Assessment tax returns, deadlines
Late filing penalty	£100; after 3 months £10 a day up to £900; after 6 months and again after 12 months, 5% of the tax due or £300, whichever is greater	GOV.UK, Self Assessment tax returns, penalties
Late payment penalty	5% of unpaid tax at 30 days, 6 months and 12 months, plus interest	GOV.UK, Self Assessment tax returns, penalties

Do you need to file?

Tax on wages and pensions is usually deducted automatically. GOV.UK says you must send a return for the last tax year (6 April to 5 April) if, for example, you were a sole trader earning more than £1,000 before reliefs, a partner in a business partnership, or you had to pay Capital Gains Tax. You may also need to send one for untaxed income, such as rent, savings interest, dividends or foreign income. You must also send a return if HMRC asks you to.

For people with income from abroad, GOV.UK says UK residents with foreign income or capital gains usually need to fill in a return and use its “foreign” section. You don’t need to if your only foreign income is dividends, your total dividends (UK and foreign) are below the £500 dividend allowance and you have no other income to report.

The order of steps

Register for Self Assessment by 5 October after the end of the tax year in which you had the income. HMRC then writes to you with what to do next.
File after the tax year ends on 5 April: on paper by 31 October, or online by 31 January.
Pay by 31 January. If you make payments on account, there is a second payment deadline on 31 July.

GOV.UK warns that if you register after 5 October and do not pay all your tax by 31 January, you may get a “failure to notify” penalty, based on the amount still unpaid.

Correcting a return

GOV.UK says you can correct a return within 12 months of the Self Assessment deadline, online or by sending another paper return. After that, you need to write to HMRC.

Claims for the 4-year foreign income and gains regime and Overseas Workday Relief are made in the Self Assessment return (HMRC guidance on each).
GOV.UK lists commercial software as a way to send a return in some cases, including if you lived abroad as a non-resident.

Sources

GOV.UK: Self Assessment tax returns (sections: who must send a tax return, deadlines, penalties) checked 2026-10-25
GOV.UK: Check how to register for Self Assessment checked 2026-10-25
GOV.UK: Tax on foreign income, Reporting your foreign income checked 2026-10-25

Change history

2026-10-25: Page created

This is general information, not legal advice, and Lumen is not a law firm. Rules change and offices differ: check the official sources above before you act. Found something wrong or out of date? Write to support@lumen.observer.