Written by Hammad Rasool MAAT·AAT licensed accountant·Updated November 2026

What the SA250 is

When you register for Self Assessment, HMRC sets up a record and posts you a letter, usually marked SA250, containing your Unique Taxpayer Reference (UTR). The UTR is 10 digits long and stays with you for life. You need it to file a tax return, to pay your bill and to authorise an accountant.

How long it takes

GOV.UK says the UTR is posted to you and normally arrives around 15 days after you register. It can take longer if you live abroad. If you set up a Personal Tax Account or use the HMRC app, you can often see the number there sooner.

Where to find your UTR if you lose the letter

  • In your Personal Tax Account or the HMRC app.
  • On previous tax returns.
  • On other letters from HMRC about Self Assessment, such as a notice to file a return or a payment reminder.
Keep it private: your UTR is used to identify you to HMRC. Do not share it on social media or with anyone who contacts you out of the blue. Agencies that charge a fee to "apply for a UTR" are doing something you can do free on GOV.UK.

What to do once it arrives

  1. Store it safely: keep the letter with your tax papers and save the number somewhere secure.
  2. Set up your online account: you need a Government Gateway login to file online. HMRC posts an activation code, so do this well before the deadline.
  3. Note your first deadline: for the 2025/26 tax year, the online return and the tax are both due by 31 January 2027.
  4. Start keeping records now: income, expenses, mileage and bank statements from the day you started trading.
  5. Budget for the first bill: your first bill can include a payment on account towards the following year, which can make it up to 50% larger than people expect.
Example

Bilal started driving for a delivery app in June 2025 and registered for Self Assessment in September 2026. His SA250 arrived about 2 weeks later. His first return, for 2025/26, is due by 31 January 2027, so he has roughly 4 months to gather his income statements and mileage log.

If no letter arrives

Check your Personal Tax Account or the HMRC app first. If the number is not showing there, you can ask HMRC to send it again by post. HMRC will not give a UTR out by phone to someone who cannot pass its security checks.

Common questions

How many digits is a UTR?
10 digits. It sometimes appears with the letter K at the end on HMRC paperwork.
Is the UTR the same as my National Insurance number?
No. Your National Insurance number identifies you for contributions and benefits. The UTR identifies your Self Assessment record.
Do I get a new UTR if I stop and restart self employment?
No. You keep the same UTR for life. You register again and HMRC reactivates the same record.
Does a limited company have its own UTR?
Yes. A company gets its own 10 digit UTR for Corporation Tax, separate from the personal UTR of its directors.

Checked against GOV.UK on 10 November 2026: Find your UTR number, Register for Self Assessment.

About the author

Hammad Rasool MAAT is an AAT licensed accountant based in Bolton. TaxTune Accountants looks after sole traders, landlords, contractors and limited companies in Bolton, Wigan, Bury, Salford, Oldham, Stockport and Manchester, and online across the UK.