What is incumbent upon one who did not pay Zakat al-Fitr for some reason, and is it permissible for him to pay it now?

Zakat al-Fitr is obligatory for every Muslim on behalf of himself and those whose maintenance is his responsibility, provided that what he possesses exceeds his and his family's sustenance for the day and night of Eid. It must be paid before people go out for the prayer, because the Messenger of Allah (peace and blessings of Allah be upon him) "enjoined Zakat al-Fitr: a sa' of dates or a sa' of barley upon the slave and the free, the male and the female, the young and the old among the Muslims, and he commanded that it be paid before people go out for the prayer." Therefore, leniency in paying it or delaying it beyond its mentioned time is not permissible, and the one who does so is sinful unless there is a legitimate excuse. If the delay is due to an excuse, there is no sin; otherwise, one must seek forgiveness and repent.