A1 for employee in the UK and self-employed in EU

I am an employee of a LTD based in the UK, and I live in the UK, but recently became an owner of a LTD in Bulgaria. I am the only director an self-employed there. I was asked by the Bulgarian tax office to provide A1 certificate. So far I have found two forms : CA3837 - I get to a point where I need to provide self-employment dates for the UK and I am an employee, CA3837 - i need my employer to send me abroad and that's not the case. Is there any other forms ? I will be working online while living in the UK, so no travel is included.

Hi,
The correct form to complete when employed in the UK and self employed abroad would be the CA8421.
You can find this online at:
Apply for a certificate to confirm you pay UK National Insurance when working in 2 or more countries (CA8421)
Thank you.