What is the ruling on someone who leads the Maghrib prayer and forgets to recite aloud?

The majority of scholars hold that it is sunnah (recommended) for the Imam to recite aloud in audible prayers and silently in silent prayers. However, the Hanafis made it obligatory for the Imam to recite aloud in audible prayers and silently in silent prayers, and violating this necessitates prostration of forgetfulness (sujud al-sahw). The Malikis agreed with them on its recommendation but did not agree with them on considering audible and silent recitation obligatory. There is no prostration of forgetfulness according to the Shafi'is and Hanbalis.

As for the individual praying alone, it is sunnah for him to recite aloud in audible prayers according to the Malikis and Shafi'is, while he has the choice between reciting aloud or silently according to the Hanafis and Hanbalis.

As for the one praying behind an Imam, it is disliked for him to recite aloud behind his Imam, whether in an audible or silent prayer.