Is profit from selling a residential house subject to zakat immediately after the sale or only after a full year, and can zakat be used to settle one's own debts?

Summary

If a person owns many houses and regularly sells them, the sales are treated as business zakat, which falls due after one full year. Whether the profit is joint marital property depends on discretion and custom, and if the wife was directly involved it is considered such; the matter is recommended to be referred to the syariah court. The ruling prefers keeping the payment of zakat separate from the settlement of debts, to avoid disagreement and the appearance of using personal zakat money to pay personal debts.

Written in our own words from the original fatwa — check the source before acting on it.