The VAT registration in Bulgaria for a EU Foreign company will be something which can happen without any additional problems from the National Revenue Agency. The registration itself takes 14 days.
Regarding the VAT registration, the needed documents are as follows:

1. Only for the manager of the company: a claim for issuing of personal identification number (a special form which we will prepare).
2. Claim for issuing of identification number for the company (another special form NRA we will prepare).
3. Application form for the VAT registration. (another special form NRA we will prepare).
4. Declaration under art. 74 signed by the manager. In general here you have to declare that you have no criminal proceedings against the tax system. (a special form which we will prepare and send to you for signing).
5. Turnover report for the last 12 months; (a form which we will prepare).
6. Application and declaration under art. 101 p. from 5 VAT Act – with this document you inform the Bulgarian National revenue agency about your official e-mail address. In case of change you have to inform the NRA about it within 7 days. (a form which we will prepare and send to you for signing).
7. Official (signed and stamped) document by the authorized Greece Agency for the main activity of the company.
8. Certified Certificate (official) from the Chamber of Commerce in Greece if such registration exists – provided by the company.
9. Translation and legalization of a Certificate of current status and the Company Tax Registration Certificate (in Greece).
10. Power of attorney for the person who has to submit the above mentioned documents.

Note: All documents in a foreign language are to be translated into Bulgarian by a sworn translator