How many months old can a baby suitable to sit on bumper chair ?

good neck control and being able to sit with some assistance will be a good time to put in a chair. always ensure that whatever chair u are using is safely secured and if it is not a heavy chair then have to be beside baby all the time incase it topples. i would put the chair in a soft environment too and never turn ur back to baby - or at least not for too long in case anything happens yar.