Q:

I have a question. If  an unmarried a woman dies while her some fasting or zakat are due, is it enough for her brother or his wife or his children or other person outside family to make up fasting or pay remaining zakat as there are no heir or  guardians of her are not here? 

A:

In the Name of Allah, the All-Merciful, the Mercy-Giving.

All praise is due to Allah. Peace and blessings be upon His Prophet Muhammad.

Regarding Zakah, if it had become due on this woman before her death, then the due amount of Zakah has to be paid out of her inheritance. So, it is the duty of her heirs to give it out.

Regarding fasting, if she had no time to make up the obligatory days she missed (she kept sick till she died, for example), then she has become free from liability and there is no need to make these days up.

However, if she had time to make them up but she did not, then her relatives may make them up instead. The Messenger of Allah (peace and blessings be upon him) said, “Whoever dies with [days of] fasting due on him his wali (heir/relative) may make them up instead.” (Al-Bukhari and Muslim)

If her relatives do not want to make them up, they may give food to an indigent person for each day instead out of this woman’s inheritance. The relatives may also authorize a non-relative to do either of these two options.

According to one juristic opinion, a non-relative may do either of the two options even without authorization from the relatives. This opinion quotes as a supportive evidence the case of the woman who came to the Messenger of Allah (peace and blessings be upon him) asking him if she could make up fasting on behalf of her dead mother. The Messenger of Allah asked, “If she were in debt, would you pay it out on her behalf?” She said, “Yes.” He said, “The debt owed to Allah is worthier to be paid.” (Muslim)

The proponents of this opinion argue that the Messenger of Allah (peace and blessings be upon him) considered fasting as a kind of debt and rules dictate that a debt might be paid by anybody.

Allah knows best.