Is it permissible to pay charity (sadaqah) or zakat to a person who is unable to pay off his debt and the due date has arrived, and he has no financial resource other than his salary, and he has children, and must he be informed that it is zakat or sadaqah?

It is permissible to give Zakat to the indebted person, as he is one of the eight categories, and he must be informed that it is Zakat because he is entitled to it on that basis.

The indebted person receives Zakat with a conditional understanding: if he spends it on the purpose for which he became entitled to receive it, then it is fine; otherwise, it must be reclaimed from him. It is permissible for him to invest what he received from Zakat if it is not sufficient to repay the debt, in order to grow it.

As for charity (sadaqa), there is no need to inform the recipient that it is charity.