Is it permissible for the husband to consider the money he pays his wife as daily expenses against her deferred mahr?

If the deferred mahr (dowry) has a specified due date, then you have the right to claim it upon its arrival. If it does not have a specified due date, then its due date is death or separation. However, if the due date is unknown, the preponderant opinion is that such a date is invalid, and the mahr becomes immediately due. The husband must pay the deferred mahr upon its due date, and the non-deferred mahr immediately. The obligatory maintenance (nafaqa) upon the husband is a sufficient amount for food, housing, and clothing. He is not obligated to give extra pocket money, but doing so is an act of kindness. The husband is not permitted to count any additional amount he gives to his wife as part of the deferred mahr without her knowledge and consent.