Is Zakat obligatory on money paid to the bank in installments for my brother's loan, knowing that the money was not returned until after five years, and what is the amount that must be given out?

You must repent to Allah from usurious transactions, because every loan that yields a benefit is usury. The lender, the borrower, and everyone who assists in it share in the sin, for "the Messenger of Allah, peace and blessings be upon him, cursed the one who consumes usury, the one who feeds it, its scribe, and its two witnesses, and he said: 'They are all equal.'"

Regarding zakat, it must be paid annually on wealth subject to zakat, such as banknotes and trade goods. This includes the debt owed by the brother if he is solvent and not procrastinating. Usurious interest, however, is excluded because it is unlawful.

If the questioner possesses non-zakat-eligible assets exceeding his needs (such as real estate or vehicles not intended for trade), he should consider the excess amount against the debt and pay zakat on the entire wealth without deduction. If he does not have such assets, he should deduct the equivalent of the debt from his wealth and pay zakat on the remainder if it reaches the threshold.

If the questioner has not paid zakat in previous years, assuming that the loan prevented it, he must promptly pay it for those years.