Hi,
You can apply for a statement of UK National Insurance contributions while you are still living and working in the UK. You would request this by completing application form CA3916.
Get a statement of your National Insurance contributions (CA3916)
You would choose the option to apply for a Statement of National Insurance contributions rather than a U1 statement. A U1 statement is required by the authorities in the country you are going to, to assist you with a claim to unemployment benefit in that country. It can only be applied for after you have left the UK (or if you are within 2 weeks of your date of departure).
If you are having problems completing the application for a statement of National Insurance contributions, you can contact the online services helpdesk who will be able to assist you.
Technical support with HMRC online services
You can call them using the number in the link above. However, the Statement of National Insurance contributions would not be proof that you are health insured in the UK. It is for information purposes only.
If the Bulgarian Authorities require proof that you are health insured in the UK, they would need to request a S041 certificate from HMRC. They would request this by submitting a S040 application. This has to be requested by the Bulgarian Authorities, you cannot request this certificate.
Thank you.