Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) was asked:
Is zakaah better in Ramadaan, even though it is one of the pillars of Islam?
Zakaah, like other good deeds, is better when done at a time of virtue, but when zakaah becomes obligatory and the year has passed, it becomes obligatory for a person to pay it, and he should not delay it until Ramadaan. If the year is completed in Rajab, then he should not delay it until Ramadaan, rather he should pay it in Rajab. If the year is completed in Muharram then he should pay it in Muharram, and not delay it until Ramadaan. But if the year is completed in Ramadaan, then he should pay it in Ramadaan. End quote.
Fataawa Islamiyyah, 2/164