With regard to the reward which is mentioned in the hadeeth for the one says Ameen at the same time as the imam and at the same time as the angels, is the one who says ameen before the imam included in this?.
Praise be to Allaah.
The person who says Ameen before the imam is not included in
that reward, because the Prophet (blessings and peace of Allah be upon him)
said: “whoever (says Ameen) at the same time as.” But if we assume that the
imam delayed it, in that case there is nothing wrong with the person who is
praying behind him saying Ameen. End quote.
Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him).