Self Assessment reminders: registration, reactivation, deregistration and agent authorisations

We are just under 3 weeks away from the 5 October deadline for notifying HMRC about untaxed income for the 2024-25 tax year, and HMRC have asked us to share the following reminders with our members.

Registering for Self Assessment

Use the online forms on GOV.UK to register your clients for Self Assessment.

Reactivating accounts

If your client has previously been in Self Assessment and didn’t submit a tax return last year, make sure their account is reactivated before submitting their 2024-25 tax return. They do not need to register again, as they will already have a Unique Taxpayer Reference number (UTR).

To reactivate their account, use the CWF1 or SA1 online forms.

Why registration and reactivation matters

Submitting a tax return without registering or reactivating an account can delay processing, lead to incorrect tax calculations, or trigger repayments that HMRC will need to recover.

Agent authorisation

Make sure your clients complete the 64-8 online form and it includes the correct agent code so HMRC can link the customer to the agent. Using HMRC’s online service is quicker, but if you can’t use it, you can complete a paper form and post it to HMRC.

No longer need to submit a tax return?

Tell HMRC as soon as possible. If a tax return isn’t submitted, then a penalty may be issued.