Document, that i pay taxes in Belgium - where from

Hi all,
I came to Brussels several months ago and i am registered as self-employed here and i start paying my taxes here.
But as i come from Bulgaria, the authorities there told me, that i have provide EU formular 4 (old name, do not know how is it called now) to verify that i pay taxes here.
Does anybody know from where i can obtain this document?

Regards,
Ivaylo

Visit your local commune and ask ?

Hello,

Have a look on this website http://finances.belgium.be/en or take contact with this organization http://www.ucm.eu/