Does the intention (for Zakat) have to be made at the time of its disbursement, or is it valid if a man informs his wife afterwards that he paid Zakat on her behalf?

For the Zakat to be valid, the intention must accompany the act of giving it or precede it by a short time. If Zakat is given on behalf of the wife without her permission, and she is informed of it later, the Zakat is not valid for her.