[Zakāh on a Woman’s Dowry If She Does Not Receive It Until After Years]

Answer—and Allah is the One who grants success: Among the scholars are those who hold that there is no zakāh on the dowry if it was a debt upon the husband, among them Imām al-Manṣūr biʾllāh al-Qāsim b. Muḥammad—peace be upon him—and other Imāms—peace be upon them.
Accordingly we say: she pays zakāh for one year—one quarter of a tenth—and she is not required to pay for any other years. This may be evidenced by several points:
1. What Imām al-Qāsim b. Muḥammad—peace be upon him—mentioned: that the dowry is a grant (niḥlah), and a grant is a gift; there is no zakāh on a gift.
2. That with the passing of years, the time for zakāh has lapsed; and the issue is one of scholarly disagreement.
3. What the jurists of the school said: the madhhab of a layperson is the madhhab of whomever she follows; thus the madhhab of that woman, regarding the years whose time has lapsed, is the madhhab of al-Qāsim b. Muḥammad.
4. What is narrated from some scholars of the Prophet’s Household—peace be upon them—that a layperson may follow whomever he wishes among the scholars of the Prophet’s Household—may Allah exalt them—without distinction between one already committed (to a jurist) and one who is not.
If it is said: Why did you oblige her to pay zakāh for one year only and not for the remaining years?
We say: We only obliged her for one year because the time for zakāh of that year has not lapsed; and we dropped the zakāh of the other years because the time for their zakāh has lapsed.
Source : Min Thimār al-ʿIlm wa al-Ḥikmah vol.1