Can the rent due from a poor tenant be considered as zakat if it is not collected?

For zakat to be valid, it is required that the money or goods to be given to the poor person are actually transferred to their ownership. This is fulfilled by physically delivering the zakat to the poor. (Ibn Abidin, Radd al-Muhtar, 2/369) For example, simply preparing food and announcing that the poor may eat it, or feeding it to them, does not constitute a transfer of ownership. However, if the same food is prepared and handed over to the poor with the intention of zakat, the transfer of ownership takes place and zakat is considered given. Accordingly, if a person gives a loan without the intention of zakat, and later decides to count that money as zakat, since the money itself is no longer present, the transfer of ownership does not occur. Therefore, forgiving a debt that was previously given as a loan to someone, with the intention of zakat, does not fulfill the zakat obligation. Scholars of all four madhhabs share this view.

However, some scholars who interpret the concept of transfer of ownership (tamlik) more broadly have considered the act of forgiving a debt such as rent owed by the poor as a valid form of transfer, and have deemed it permissible. (Qaradawi, Fiqh al-Zakat, 3/325-326; Zuhayli, al-Fiqh al-Islami, 3/1981) It is also permissible to act according to this latter opinion.

Source: T.C. Diyanet İşleri Başkanlığı, Din İşleri Yüksek Kurulu