Rizwan and Irfan both suffered hamstring injuries in the third match in Rawalpindi, where a second-string New Zealand side won by seven wickets to level the five-match series 1-1
One demerit point has been added to the disciplinary records of each of the players.
Mahmudullah, an experienced Bangladeshi cricketer, was fined 10 percent of his match fee, while pacer Boult was fined 15 percent.
They were found guilty for two separate incidents. Mahmudullah was fined for striking the picket fence with his bat while leaving field after he was dismissed. Boult was found guilty for vocalising obscene words audibly twice during his bowling.
The two accepted the sanctions against them. There was no need for a formal hearing.
It is the first ever fines since the new code of conduct for cricket passed in 2016.