Return of ay 11-12 filed in itr form of ay 12-13 ?

Hello everyone,

i wanted to file ay 11-12 return of one of my client but due to last date (return was filed on 31/07/12) hurry my assisstant used the itr form of a.y. 12-13 and filed the return manually.

How should i rectify this mistake ?

waiting urgently for your reply.