The Ruling on Sadaqat al-Fitr
Sadaqat al-Fitr is Waajib on every free Muslim who, after the requirements of his fundamental needs, is the owner of Nisaab, irrespective of whether a year has passed or not (on his ownership of the Nisaab). Such a person must give Sadaqat al-Fitr on his own behalf, on behalf of his minor children and the slaves in his service.
The time for when Sadaqat al-Fitr becomes Waajib is the time of the dawn (Fajr Saadiq) on the day of Eid al-Fitr. Sadaqat al-Fitr is not Waajib on the person who dies before this time. Similarly the person who is born or accepts Islam after this time, Sadaqat al-Fitr is not Waajib upon him.
It is Mustahabb (desirable) that people should pay Sadaqat al-Fitr before setting off for Eid prayer on the day of Eid al-Fitr. It is permissible to pay Sadaqat al-Fitr before the day of Eid al-Fitr. If people do not pay it on Eid day they will still have to pay it after wards, the responsibilty does not drop.