Dr. Muzammil Siddiqi, former president of the Islamic Society of North America (ISNA), states the following: “It is the duty of the person who gives Zakah to make sure that his/her Zakah reaches the deserving people according to the rules of the Shari`ah.
If knowingly or due to negligence the Zakah is given to a person who does not deserve it, then the Zakah is not paid and one has to pay it again.
However, if the mistake was not deliberate then the Zakah is paid. When paying Zakah through Zakah collecting agencies, relief organizations or Islamic centers, one should make sure that they distribute it according to Islamic principles. Once the Zakah is given through reliable and trustworthy institutions it is paid.”