Answer
A complex crime under Article 48 of the Revised Penal Code arises in two situations: (1) when a single act constitutes two or more grave or less grave felonies (a compound crime), and (2) when an offense is a necessary means for committing another (a complex crime proper). In both, although several felonies are involved, the law treats them as one for the purpose of imposing the penalty.
In a complex crime, the penalty for the most serious component offense is imposed in its maximum period. This is generally more favorable to the accused than being penalized separately for each felony. The concept is distinct from a special complex crime — such as robbery with homicide — where the law itself prescribes a single specific penalty for the combination.