Ibn 'Umar said that the Messenger of Allah (ﷺ) prescribed Zakat-ul-Fitr one sa' of dates or one sa' of barley for every slave or freeman, young or old.

Sadaqatul Fitr/Zakat ul Fitr

Sadaqatul fitr (also known as zakaat ul fitr or fitrana) must be paid before the Eid prayers, preferably at least a few days before so it can reach the people in need in time for Eid. It is a duty on every sane Muslim who possesses the value of nisab beyond their basic necessities. For young children who possess the value of nisab, fathers must pay on their behalf. 

If one does not pay the sadaqatul fitr, it will remain due on them until they have fulfilled this duty. 

Sadaqatul fitr is currently set as £4 per person