How is the zakat threshold (nisab) calculated for a couple, is it permissible for the husband to pay his wife's zakat on her money, and is it permissible to delay or advance the payment of zakat on money due to circumstances?

The co-owned wealth of a husband and wife, excluding livestock, can take two forms: The first: The two assets are commingled. There is a difference of opinion among scholars regarding this. The Hanafis, Malikis, Hanbalis, and the Shafi'is in their old view held that commingling is not considered, so there is no zakat until each person's share reaches the nisab. The Shafi'is in their new view held that commingling does have an effect, so zakat becomes obligatory if the wealth reaches the nisab through commingling. The second form: The two assets are not commingled. In this case, for zakat to be obligatory, it is stipulated that each person's wealth must reach the nisab and a full year must pass over it. It is permissible for the husband to pay zakat on behalf of his wife with her permission.