I worked for a full year and paid all the NI but still have gap in the NI record.

I have a full time job and work for a full year. My employer deducted the income tax and NI from my salary. Also, I have some rental income and did the self assessment and paid all the tax and NI. However, the NI record still said I have a gap. May I know is there any reason why does this happen? Thanks

Hi TFS,
If you have paid NI in every payslip in a tax year 06 April to the 05 April into the next year and without a break in employment, then you should be covered for National insurance.
If your pay fluctuates then this may affect your qualifying tax year. The self-assessment record may also need to be checked by an advisor.
Please contact the national insurance helpline so they can investigate the tax year for you.                                
If you have access to a Personal tax account, you can view your NI record and chat to an advisor through our web chat services.
Number - 0300 200 3500
Overseas - +44 191 203 7010
Open - Monday to Friday: 8am to 6pm Closed on Saturdays, Sundays and Bank Holidays.
Thank you.