How to Register for Self Assessment: UK 2026/27 Guide

Register for Self Assessment through GOV.UK if you need to file and are not already within the system. The normal notification deadline is 5 October after the end of the tax year in which the filing reason arose. Registration creates or reactivates a tax record and provides access to online filing.

Check whether registration is needed

Common reasons include:

• gross self-employment income above £1,000;
• taxable property income not fully dealt with elsewhere;
• partnership membership;
• untaxed savings, dividends, foreign or miscellaneous income requiring a return;
• chargeable capital gains;
• High Income Child Benefit Charge or certain pension charges;
• HMRC issuing a notice to file.

Use HMRC’s checker for the tax year. A return can be required even when no tax is ultimately due.

Registration deadline

Tell HMRC by 5 October following the end of the tax year. For a filing reason arising in 2026/27, the normal notification deadline is 5 October 2027, and the online return deadline is 31 January 2028.

Registering as self-employed

1. Create or sign into a Government Gateway account.
2. Use the GOV.UK service for Self Assessment and Class 2 National Insurance.
3. Provide the trading name, start date, business address and activity.
4. HMRC issues or confirms the Unique Taxpayer Reference.
5. Enrol for the online Self Assessment service where necessary.
6. File and pay by the deadline.

Registering for another reason

If you are not self-employed—for example, a landlord or person with untaxed foreign income—use the relevant SA1 or online route. Partners use separate registration and the partnership itself needs a partnership UTR.

Do you already have a UTR?

A previous Self Assessment taxpayer normally keeps the same 10-digit UTR. Do not create a duplicate registration merely because filing stopped for several years. Use HMRC’s reactivation route and confirm the address held.

Government Gateway versus UTR

They are different:

• UTR: identifies the taxpayer in Self Assessment;
• Government Gateway user ID: sign-in credential for online services;
• National Insurance number: identifies the individual for NI and related records.

Keep all credentials secure and never share authentication codes with an adviser.

What information is needed?

• National Insurance number;
• full name, date of birth and address;
• contact details;
• UTR if one already exists;
• reason registration is required;
• self-employment start date and activity;
• partnership UTR where relevant.

How long does registration take?

Allow time for HMRC processing and postal security details. Register well before 31 January. Filing and payment deadlines are not automatically extended because registration was late.

What if the 5 October deadline was missed?

Register immediately. Failure-to-notify penalties depend on unpaid tax, behaviour and disclosure rather than a fixed automatic amount in every case. If all tax was paid by the due date, potential lost revenue may be nil, but filing obligations remain.

Notice to file

If HMRC sends a notice, submit the return unless HMRC withdraws it. Registering is not the same as filing. Ignoring a notice can trigger late-filing penalties even where HMRC already holds PAYE data.

After registering

• confirm the UTR and online access;
• collect records for all income and claims;
• check payments on account;
• set 31 January and 31 July reminders;
• review MTD for Income Tax eligibility;
• authorise an agent through HMRC if using one.

Making Tax Digital

MTD for Income Tax begins from April 2026 above £50,000 qualifying income, April 2027 above £30,000 and April 2028 above £20,000. Self Assessment registration alone does not complete MTD sign-up; eligible taxpayers must use the designated process and compatible software.

Official guidance

• HMRC: register for Self Assessment
• HMRC: check if you need a return

This guide is general information. Use the registration route matching the actual filing reason.