Reminder: 5 October deadline to register for Self Assessment

If you had new income during the 2025/26 tax year that HMRC does not already know about, you may need to register for Self Assessment by 5 October 2026.

This deadline often catches people out precisely because it applies to those who do not think of themselves as needing to file a tax return.

It is not about filing or paying, instead it is about telling HMRC whether a tax return is needed at all.

This deadline applies to:

• Anyone who became self-employed during 2025/26 and has not registered before.
• Landlords with new rental income to declare for the first time.
• Anyone with other untaxed income, such as dividends, or a household affected by the High Income Child Benefit Charge for the first time.
• Anyone who stopped filing a return in previous years but now has income that brings them back within Self Assessment.

If you have filed a Self Assessment return for the previous tax year already, you do not need to register again.

HMRC will continue to expect a return from you each year until you formally leave Self Assessment.

Why it is worth acting now

Registering late does not stop you from filing, but it is treated as a failure to notify and can lead to a penalty geared to the tax eventually found to be owed, even where the amount involved is modest.

Registering also takes time to process. HMRC issues a Unique Taxpayer Reference once registration is complete and this can take a couple of weeks to arrive by post, so leaving it until close to the deadline adds unnecessary pressure ahead of the 31 January filing date.

If you think you may need to register for Self Assessment for the first time, or are not sure whether your circumstances require it, contact us well before 5 October and we will take care of the registration for you.