Self Assessment: Do You Need a National Insurance Number?
You need your National Insurance (NI) number to register for Self Assessment and to file your return. It is a unique personal identifier used across all government services.
Where to Find Your NI Number
- On your payslip or P60
- On letters from HMRC
- On your National Insurance card (if you still have it)
- In your HMRC online account
- On the HMRC app
If You Cannot Find It
Call the National Insurance helpline on 0300 200 3500. You will need to verify your identity, and they can confirm your number over the phone or send it by post.
Why You Need It
Your NI number links your Self Assessment to your National Insurance record. This ensures your self-employment contributions (Class 2 and Class 4 NI) are recorded correctly, protecting your State Pension entitlement and benefit eligibility.
Accounted stores your NI number securely for use in HMRC submissions.
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Tax & Compliance Specialists
Our tax specialists have decades of combined experience in UK sole trader and small business taxation, MTD compliance, and HMRC submissions. All content is reviewed against current HMRC guidance before publication and updated quarterly to reflect legislative changes.
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