Hi
The 3 additional years on top of the 9 you have fully paid may be what are called Juvenile Credits.
Tax payers who reached the age of 16 before April 2010 were given automatic class 3 Juvenile credits for tax years they were 16, 17 and 18 years of age.
This applies if you were living outside the UK at the time as well.
However you can contact our customer helpline or webchat to get a more precise answer.
Please find our contact details below:
National Insurance Enquiries helpline
Thank you.