Is it permissible to change the intention of giving money to a needy person from a loan to Zakat al-mal, especially if the debtor evades repayment and there is no proof of the debt? And is it necessary to inform the debtor of this? And is it permissible to count the amount as Zakat for two years if it exceeds the amount of Zakat for the current year?

Waiving a debt with the intention of it counting as Zakat is not permissible according to the majority of scholars. Therefore, it is not valid to waive a debt owed to you by a debtor with the intention of it being your Zakat payment. However, if you have already given money to the poor with the intention of it being Zakat, then it is sufficient as Zakat, provided that you had that intention before giving it, based on the Prophet's (peace be upon him) saying: "Deeds are only by intentions." Granting a respite to the one in hardship is obligatory, and waiving a debt for them is among the best forms of charity.