Question:

A person who was eligible to receive Zakat was given Zakat money. However, after some time, the eligible person returned the money due to the absence of a need. How is it for the mazakki (one who paid Zakat) to accept it?

Answer: حامدا ومصليا ومسلما

Zakat would be considered paid once it reaches the hand of the person whom it was given to on the condition that he was eligible to receive Zakat. He has become the owner. Now if he returns it then the muzakki (one who gave Zakat) should not accept it.

And Allah Ta’ala knows best.
(Hazrat Mufti) Ahmed Khanpuri (May Allah preserve him.)
Mahmoodul Fatawa Vol.2 Pg.28