Grouping assembly of coin validation and return/payment mechanisms, in such a way that said compact assembly is useful to be included in automatic vending machines and especially recreative prize machines. In this way the assembly (1) comprises a coin selector (2) with a top duct (3) for conveying the coins from the coin slot of the machine to the selector (2), some deposit tubes (4) of the coins for payment, a remover (5) of the coins from the deposit tubes (4), a coin separator (9) for separating the coins towards two money boxes (10) and (11) and a lifting mechanism (7) for conveying the coins to be returned/paid to the receiving box of the machine connected to a small top duct (8) arranged close to the top duct (3) for conveying the coins to the coin slot of the machine to the selector (2).