All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
It is worth mentioning that the Iftaa` Board has issued Resolution No.(95) clarifying the ruling of Sharia on Zakat-ul-Fitr. As indicated in the texts of Sharia, Zakat-ul-Fitr is obligatory; rather, a Muslim who delays it deliberately is considered sinful and should repent and make up for it. This is because it is an act of worship just like prayer, and should be made up for, even if its time had passed. However, the person`s fasting is considered valid. Moreover, the majority of the Muslim scholar`s are of the view that it is permissible to give Zakat-ul-Fitr on the day of Eed, but not after the sunset of that day.
Al-Shirazi (May Allah have mercy on him) said: "It is recommended to give it before Eed prayer as indicated by the Hadeeth narrated on the authority of Ibn Omar who reported that the Messenger of Allah (PBUH) ordered that the Sadaqat-ul-Fitr should be paid before the people go out for prayer. It isn`t permissible to give it after the day of Eed i.e. after the sunset of that day because the Prophet (PBUH) said: "Spare the poor the trouble of asking for charity on that day"{Al-Baihaqi}. Therefore, a person who delays Zakat-ul-Fitr after Eed day is considered sinful and he is obliged to make up for it because it is a right to the poor that isn`t waived by the passing of time." {Al-Majmou` Shareh Al-Mohazab, 6/126}.
Al-Imam An-Nawawi (May Allah have mercy on him) said: "Shafiis and fellow scholars are of the view that it is better to give it on the day of Eed, before going out for prayer, and it is also permissible to give it at any time of that day i.e. till sunset. They also said that it isn`t permissible to delay it after the day of Eed, and one who does so is considered sinful and is obliged to make up for it. Moreover, they have called giving it after the day of Eed a make up for it."{Al-Majmou`,6/84}. And Allah knows best.