Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.

 

Mahr is the bridal gift and the right of a woman in marriage. It can be anything of value as long as it is mutually agreed. Since it is her right, if your wife agrees that you may you deduct it from the money she owes you, it is fine.

 

However, since marriage is a happy occasion, it would be better if you volunteer to give her a gift rather than deducting the amount from the debt she owes you.

 

We should remember that the foundations of a successful marriage are: trust, altruism, and compassion.

 

Allah Almighty knows best.