Response: Discharging the Zakaatul-Fitr before the (`Eed) prayer is obligatory, and whoever forgets then there is nothing upon him except to discharge it after that. This is because it is an obligation so it is upon him to discharge it when he remembers, and it is not permissible for anyone to intentionally delay it until after the `Eed prayer according to the most correct of the two opinions. This is because the Messenger (sal-Allaahu `alayhe wa sallam) commanded the Muslims to discharge it before the `Eed prayer.
Shaykh Ibn Baaz
Fataawa Ramadhaan – Volume 2, Pages 931-932, Fatwa No. 914;
Majmoo’ Fataawa Samaahatu ash-Shaykh ‘Abdul Azeez Ibn ‘Abdullaah Ibn Baaz – Volume 3, Page 101.fatwaonline.com