If wealth dips below the nisaab during the year

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Does a woman have to pay zakaah on the second part of the dowry?
Paying zakat on total wealth not just the amount greater than nisaab

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Related Answers:
Does he have to pay zakaah on money which his father is saving for him?
Zakaah on money that is set aside for buying a house
It is not permissible for the guardian to dispose of wealth belonging to the one who is under his guardianship, except in a manner that will most likely be in the latter’s best interests
Does a woman have to pay zakaah on the second part of the dowry?
Paying zakat on total wealth not just the amount greater than nisaab

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