The Bottom Line
- You apply online for a National Insurance (NI) number and must prove your identity as part of the process.
- You can usually start work before your NI number arrives if you can prove your right to work—tell HR you have applied and share proof.
- Most payroll problems come from missing/incorrect personal details: name spelling, date of birth, address, and right-to-work status. Fix those early.
The “NI number” purpose
Your NI number links your earnings to tax and National Insurance contributions. It becomes part of your long-term UK admin identity (payroll, pensions, HMRC records).
Apply for an NI number (fast, correct, minimal drama)
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1) Confirm you are eligible
You must live in the UK, have the right to work, and be working/looking for work/have an offer to start work.
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2) Apply online
Use the official GOV.UK application route. You will need to prove your identity—usually with passport or eligible national ID documents.
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3) Keep proof you applied
Save screenshots/emails confirming submission. HR often just needs reassurance that the application is in progress.
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4) Tell HR proactively
Don’t wait for payroll to chase you. Email HR: “NI application submitted on [date]. I can start work; I will forward the NI number immediately when received.”
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5) When it arrives, update all the systems once
Tell: HR, payroll/ESR team, and (if asked) your bank/tax admin workflow. Consistency avoids mismatches later.
Copy-paste email to HR (while waiting for your NI number)
Subject: NI number application submitted
Hi [Name], I have applied online for my National Insurance number on [date] and can provide proof of application if needed. I understand I can start work while waiting as I have the right to work in the UK. I will forward my NI number to payroll immediately once issued. Many thanks — Dr [Name].
Practice
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