Certifying NIC when applying for state pension in Bulgaria

Please advise what is the name of the form I need in order to prove my NIC in the UK when applying for state pension in Bulgaria. I applied 2 years ago and all I get from Bulgarian authorities is that they have requested this information from the UK but there was no reply from the UK authorities. Where can I check out this? Or how can I apply for such document?

Hi Alexander,
Thank you for your enquiry. You can apply for a statement of your UK National Insurance records by completing the form CA3916 which can be found here - Get a PDU1 certificate or a National Insurance contributions statement - GOV.UK (www.gov.uk).
Thank you.