GENERAL PART
VII C H A P T E R S E V E N
PUNISHMENT
Meting out Punishment of a Convicted Person
Article 55
(1) If a convicted person is tried for a criminal offence he had perpetrated before commencing to serve the previous sentence, or for a criminal offence he perpetrated while serving a sentence of imprisonment, long-term imprisonment or juvenile imprisonment, the court shall impose a compound punishment for all the criminal offences applying provisions set forth under Article 53 (Concurrence of Criminal Offences) of this Code, taking the punishment from the earlier sentence as an already fixed punishment. The sentence or part of the sentence, which the convicted person had already served, shall be credited towards the imposed sentence of imprisonment or long-term imprisonment.
(2) For criminal offences perpetrated during the course of serving the punishment of imprisonment, long-term imprisonment, or juvenile imprisonment, the court shall determine the perpetrator's punishment independently of the punishment for the earlier sentence in cases when the application of the provisions set forth under Article 53 of this Code would lead to failure to achieve the purpose of punishment considering the duration of non-served portion of the previous sentence.
Joint sentence following multiple convictions - national proceedings
EDIT.