Why I got Two NI numbers?

Dear HMRC Team, I hope this message finds you well. I have recently discovered that I possess two National Insurance Numbers (NINs), and I have also received a tax refund from HMRC. I am writing to seek guidance on how to address this situation appropriately. The details of the two National Insurance Numbers are as follows: 1. National Insurance Number 1: [NJ...] 2. National Insurance Number 2: [08...] I am concerned about the presence of two NINs and would like to rectify this issue as soon as possible. Additionally, I want to ensure that I am in compliance with tax regulations and that any refund received is correctly attributed. Could you please advise me on the necessary steps to resolve this matter? If there are specific documents or information required from my end, please let me know, and I will promptly provide them. I understand the importance of addressing this issue promptly and in accordance with HMRC’s guidelines. Your guidance and assistance in this matter would be greatly appreciated. Thank you for your attention to this matter, and I look forward to your response. Sincerely

Hi Kevin.L,

If you could send us a letter to quote both of your National Insurance Numbers we’ll be able to merge them both together so that you only have one Number which you
will keep throughout all of your life.  
Our postal address is:
 HM Revenue & Customs,
PT Operations North East England,
BX9 1AN

Thank you.

I have a slightly different but similar issue should I call or write to the the same address with the details requested ? Please advise thanks.

Hi O Alam,

You are welcome to call our National Insurance Helpline on 0300 200 3500 to ask any National Insurance questions that you might have.  
If you prefer to write to us, our postal address is
HM Revenue & Customs,
PT Operations North East England,
BX9 1AN
If you have access to your Personal Tax Account (PTA) you will be able to check your National Insurance and Pension positions which might answer your questions.  
If you don’t have access to your PTA you may set one up via Personal tax account: sign in or set up

Thank you.