It is an obligation on every Muslim who possesses enough food exceeding his or his family's basic needs for the duration of the day or night of 'Eid. Any Muslim who meets this condition has to pay Zakat-ul-Fitrah on behalf of everyone he is obliged to spend on, such as his wife, children and parents.
Ibn ‘Umar said: "The Prophet enjoined the payment of one Saa' (2,480 grams) of dates or one Saa' of barley as Zakat-ul-Fitrah on every Muslim, free or slave, male or female young or old. He also ordered that it should be paid before people go to 'Ed prayer." [Al-Bukhari]
Zakat-ul-Fitrah should be paid out of the common food in the country and it should be given to the needy and the poor. It is better if it is given out on 'Eid day but if it is given on the first day of Ramadhan then that is also sufficient.
As regards giving the value of the Zakat-ul-Fitrah instead of food, Imam Malik, Ash-Shafi’e and Ahmad are of the view that it should be given as food, not as money. However, Imam Abu Hanifah is of the view that if its value (money) is given instead of food then that is sufficient. Our view in Islamweb is in favour of the first opinion.
As for Zakat-ul-Fitrah for couples living apart, the wife is among the persons whom the husband has to provide for, so he has to pay Zakat-ul-Fitrah on her. This is the opinion of Imams Shafi’e, Ahmad and Malik. Spending on the wife is obligatory if the marriage is consummated. Just signing the contract without consummating the marriage does not obligate the husband to provide for her or pay Zakat-ul-Fitrah on her. Therefore, if the husband has consummated the marriage, or consummation of marriage was arranged and made easy for him but he failed to consummate it, then he is obliged to provide for her and pay Zakat-ul-Fitrah on her.
However, if he has not consummated the marriage or it was not made easy for him, or she refused, then he is not obliged to provide for her, or pay Zakat-ul-Fitrah on her. In any case, if he pays Zakat-ul-Fitrah on she with her permission, then that suffices her, even if he is not obliged to pay for her. Anyway, Zakat-ul-Fitrah is not a great expenditure; it is only 2.5 kilograms of rice, wheat or the like or the equivalent value of money.