Sadaqa-i Fitr

All of the following information was translated originally from Durr-ul-mukhtar, and from Ibni Abidin's Radd-ul-mukhtar, which is an explanation of the former:

By the first light of the morning of the first day of 'Iyd of Ramadan, to give the Fitra [1] becomes wajib [2] for every free Muslim who has property or money as much as the amount of nisab [3] in addition to his indispensable possessions and debts. It does not become wajib before or after that time. The property that is to be included in the calculation of nisab for fitra and Qurban does not necessarily have to be intended for trade, nor does one have to have had it for one year. The condition is that one should have property as much as the amount of nisab by the time morning prayer becomes performable on the first day of 'Iyd.

Giving the fitra is not wajib for a person who receives the amount of nisab or who is born, or becomes a Muslim after that moment. It is necessary also for the safari (traveller) to give the fitra. It is also permissible to give it during Ramadan-i-sherif, before Ramadan, or after the 'Iyd. Furthermore, if a person died before giving the fitra, zakat, kaffarat or something he vowed, and if he did not will it in his last request that it must be given, it is permissible for one of his inheritors to give it to the poor out of his own property, [not necessarily out of the dead person's property]. But the inheritor does not have to give it. If he willed that it must be given, it is necessary to give it out of a third of the property he has left behind. His will is not executed if he has not left property. There will be more blessings if the fitra is given before the 'Iyd prayer. It cannot be given before Ramadan in Shafi'i Madhhab [4] and before 'Iyd in the Madhahib of Maliki and Hanbali.

[1] fitra: alms (2 kg of wheat or silver of equal value) given after every Ramadan, the ninth month of Muslim calendar.
[2] wajib: (act, thing) never omitted by the Prophet, so almost as compulsory as fard and not to be omitted. Wajib al-wujud: Being whose existence is indispensable and nonexistence is impossible.
[3] nisab: minimum quantity of specified wealth which makes one liable to do some certain duties.
[4] madhhab: all of what a profound 'alim of (especially) Fiqh (usually one of the four-Hanafi, Shafi'i, Maliki, Hanbali) or iman (one of the two, namely Ash-ari, Maturidi) communicated.