No Zakah is due on money collected for charity
21-1-2014 | IslamWeb
Question:
My mother has an envelope which she uses for keeping the money she gives out as charity from her own money until she finds an opportunity to go out and pay it. Is Zakaah due on the money that is collected in the envelope noting that two lunar years have passed on it since she started collecting it?
Answer:
All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
Zakah is not due on money of which the owner has allocated it for charity because, by doing so, the ownership of the money is entirely transferred from the owner to those who are entitled under Sharee‘ah to receive charity. However, we notify the owner of the money in question that it is better for her to distribute it once she gets an opportunity to do so since the benefit of charity is to support the poor and fulfill their needs. Undoubtedly, keeping the money for too long may cause her to miss the time when it is suitable to be given out to those who need it. It is narrated on the authority of Abu Sirwa‘ah, ‘Uqbah ibn Al-Haarith 
that he said, “Once I performed the ‘Asr prayer in Al-Madeenah behind the Prophet, sallallaahu ‘alayhi wa sallam. He got up quickly after finishing the prayer and stepped over people, making his way to the room of one of his wives. The people were startled at his haste and, when he came out and saw their astonishment at his urgency, he said, 'I recalled that there remained some gold with me and I feared that it may hold me back (for question on the Day of Judgment), so I gave orders that it should be distributed.” [Al-Bukhari]
Another similar narration uses the wording, “I left some gold meant for charity in the house, so I disliked keeping it with us overnight.”
Generally speaking, good deeds should be done immediately and promptly.
Allaah Knows best.