Missing National Insurance number from SA800 - how do I correct?

I have completed a state pension forecast and it is showing missing years, even though I have been a partner for years submitting tax returns. I have finally got to the bottom of it - my partnership tax returns show my national insurance number is missing for a period of 9 years. The tax due on my personal account differs by the class 2 national insurance for each of those years. I have copies of all of my tax returns and SA800s - please can you advise how I can update HMRC records so that my qualifying years are correctly updated - we are now outside of the amendment period to use software. Many thanks

Hi,
If you believe that your NI/tax record may not be up to date or correct, you will need to resubmit all SA800 returns for the affected tax years.
Thank you.