A machine for forming filter bags for infusion products includes a first carousel including a plurality of first stations for operating on pieces of filtering material. A transfer device transfers the pieces to a second carousel. The transfer device includes a first wheel, rotatable parallel to the carousels, and including units for receiving from the first stations and releasing to the second carousel, the pieces. Each receiving unit includes 1) first gripping and stabilising devices for retaining the pieces upright and positioned with a free head end directed towards the axis of the first wheel and 2) second gripping devices for positioning and retaining a tag on the piece, fed from a corresponding feeding station, to release to the second carousel the piece with a corresponding tag alongside the free head end of the piece.