Self Assessment & Personal Tax
How to register for and file a UK Self Assessment tax return
Step-by-step — CWF1 / SA1 / SA401, UTR, Government Gateway, the SA100, and how to pay.
To file Self Assessment for the first time: **register with HMRC by 5 October 2026** using the right form (CWF1 self-employed, SA1 non-self-employed director/landlord, SA401 partner). HMRC posts your **Unique Taxpayer Reference (UTR)** — allow 2–3 weeks. Then set up a **Government Gateway** account, gather your records, complete the **SA100** main return online with relevant supplementary pages, and pay by 31 January. Keep records for at least 5 years after the 31 January deadline. **Read the full guide at [rraccountants.uk/how-to-register-for-self-assessment](https://rraccountants.uk/how-to-register-for-self-assessment).**
Resources
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