What is required of us after paying Zakat to the needy father of the wife for five years, based on the mistaken belief that it was permissible to do so?

It is permissible for a daughter to give her Zakat to her father if she is unable to support him, for instance, if her wealth is meager, not exceeding her needs and the needs of her children, and is insufficient for his maintenance. Giving Zakat to him is better than giving it to a stranger, for the Prophet, peace and blessings be upon him, said: "Charity given to a poor person is charity, and charity given to a relative is two: charity and maintaining kinship ties."

However, if she is capable of supporting him, then it is not permissible for her to give him Zakat. In this case, she must re-issue the amount she paid from her Zakat to the poor, because giving Zakat to someone whose support is obligatory upon her is like giving it to herself.

As for what was paid to the father from the husband's Zakat money, it is valid, because the husband is not obligated to support his wife's father.