If you are new to Self Assessment and need to submit a tax return for 2024/25, you will need to register for Self Assessment. This should be done before 5 October 2025 in order to avoid a penalty and to ensure that you receive your Unique Taxpayer Reference (UTR) and Notice to File in good time. You can either register for Self Assessment yourself or appoint an agent to register on your behalf.

If you register after 5 October 2025, you may receive a failure to notify penalty.

Check whether you need to register

You may need to register for Self Assessment if you do not currently complete a Self Assessment tax return and you had a new source of untaxed income in 2024/25. This may be the case if you started a new trade, which may include a side hustle in addition to your employment, or you started renting out property, either on a long-term let or as holiday accommodation.

However, even if you have a new source of untaxed income, you will not necessarily need to register. This will be the case if, for example, all your income from self-employment (before deductions) is less than £1,000 in the 2024/25 tax year or if your property rental income is less than £1,000 in the tax year. If you let a furnished room in your own home, there is no need to register if your rental income is less than the rent-a-room limit (£7,500 where one person receives the income or £3,750 each where more than one person receives the income).

You can check if you need to send a return by using the tool on the Gov.uk website at www.gov.uk/check-if-you-need-tax-return.

Registered before

If you have previously registered for Self Assessment but did not file a return for 2023/24, you will need to sign into the Government Gateway to reactivate your account. If you are unable to do this, you can instead complete form CWF1 and send this to HMRC.

Register online

If you need to register for Self Assessment, you can do so online by visiting the Gov.uk website at www.gov.uk/register-for-self-assessment. It can take up to 21working days for your registration to be confirmed.

File your return

The deadline for filing your 2024/25 Self Assessment tax return online is midnight on 31 January 2026. Once registered, you can file your return – you do not need to wait until January. If you miss the deadline, you will receive a late filing penalty of £100.

If you did not receive your Notice to File a return until after 31 October 2025 (but you registered for Self Assessment on or before 5 October 2025), you have until three months from the date on the Notice to File in which to file your return.

Pay your tax

You must pay any tax owing for 2024/25 by 31 January 2026. If your tax bill for 2024/25 was more than £1,000, unless 80% of your tax bill for the year was collected at source (such as under PAYE), you will also need to make the first payment on account of your 2025/26 tax liability by the same date. This is 50% of your Self Assessment tax and Class 1 National Insurance bill for 2024/25.

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Registering for Self Assessment