Yes, it is permissible to pay zakaat before its due date, because the Prophet
(peace and blessings of Allaah be upon him) accepted two years’ zakaat in advance
from al-‘Abbaas ibn ‘Abd al-Muttalib. But we should remember here that the annual
payment of zakaat is worked out according to the Hijri (Islamic) calendar, and not the
Gregorian (western) calendar – the difference between them is well known.