بسم الله الرحمن الرحيم
Q: What’s the ruling concerning he who forgets to distribute zakatul fitr, and as a result does not give it except (after remembering) during the khutbah well after the Eid prayer?
A: The distributing of zakatul fitr before the prayer is obligatory. So whoever forgets to do so there is nothing upon him besides its distribution after that (he remembers) due to it being compulsory. Thus it is binding upon him to give it after he remembers. Furthermore it is not permissible for anyone to deliberately delay giving it until after the prayer based on the most correct of the two statements (from the scholars of fiqh) because of the Messenger’s -sallahu alayhi wa salaam- command to distribute it before the prayer.
Source: http://www.alifta.net/Fatawa/FatawaChapters.aspx?languagename=ar&View=Page&PageID=61&PageNo=1&BookID=12
Translated by Najeeb ibn Yusuf Al Anjelesi