Fiqh-us-Sunnah Volume 3, Zakaat and Fasting, Fiqh 3.017.

Abu Hanifah is of the opinion that there is no zakah on the dowry of a woman until she comes to possess it. At the same time, the dowry must constitute the nisab at the end of the year. The position, however, will be different if the woman has accumulated a nisab other than the dowry. In such a case, any amount she receives should be added to the nisab, and zakah should be paid at the end of a year of possession. Ash-Shaf’i holds that a woman must pay zakah on her dowry at the end of one year, even if it is before the wedding. The probability of its restitution because of nullification, or its fifty percent refund because of divorce, does not exempt her from paying it. The Hanbaliyyah are of the opinion that dowry is a credit for women and that it is similar to debts. If the recipient of a dowry is rich, the payment of its zakah is obligatory. If the recipient is insolvent, or does not acknowledge it, then, according to al-Khiraqiyy, the zakah is obligatory regardless of the consumption of marriage. If a woman receives half of her dowry (in the case of her divorce before consumption), she should pay zakah only on the received half. However, if all of the dowry is cancelled before she receives it (in the case of nullifying the marriage on her behalf), she is under no obligation to pay its zakah.