The below might be of help? It was sent to me by my legal service who I have been with for several years with no problems, I have done exactly the same as 'saucysal' and get full copies of everything submitted and all done over the net, so I have less hassle, know its done right and have peace of mind, which suits me

NEW Amendments in the Accountancy Legislation
Starting from 1st of January 2018 the Tax Returns of companies will be submitted only online.
Other amendments to the Law on Corporate Income Tax of Bulgaria were published in the end of 2017 and according to those amendments:
Starting from 1st of January 2018 Bulgarian companies that have not performed activity according to the Accountancy Law do not submit Tax Returns and Annual Report on activity.
Instead of those accountancy reports, such companies /i.e. companies with no activity/ are obliged to publish a declaration about lack of activity at the Commercial Register.
To the present date /15th of January 2018/ there are no amendments made to the Law on Commercial Register and the Register of Non-Profit Legal Persons, which means that the exact form of the declaration about lack of activity is not yet specified but according to the official information there will be no fee of the register for publication of such declaration.
Everything said above means that:
Companies that had activity during 2017 are obliged:
- To submit a Tax return for 2017 to the National Revenue Agency no later than 31st of March 2018 as this Tax return can be submitted only online;
- To submit an Annual Report on Activity /statistical declaration/ for 2017 to the National Statistical Institute no later than 2nd of April 2018;
- To publish the Annual Financial Report for 2017 at the Commercial Register no later than 30th of June 2018.
Companies that had no activity during 2017 are obliged:
- To submit a Declaration about lack of activity /statistical declaration/ to the National Statistical Institute no later than 2nd of April 2018;
- To publish a Declaration about lack of activity for 2017 at the Commercial Register no later than 31st of March 2018.
Note: those Declarations about lack of activity are different documents and for now we cannot confirm that the declaration that should be published at the Commercial Register will look the same as the Declaration that should be submitted to the NSI.
According to the Accountancy Law companies that performed no activity during the reported period are those are enterprises that SIMULTANEOUSLY meet the following conditions:
a) during the reporting period the company has not performed deals under art. 1, para. 1 of the Commerce Act, i.e. the company has not purchased items and goods for the purpose of resale in original or processed form;
b) during the reporting period there were no conditions for recognition of an income under the Accountancy Act and the applicable accounting standards;
c) the company did not perform any activity relating to investment, production and/or sale;
d) the company did not purchase goods and services for the purpose of obtaining of income and profits.