Assalamou Aleikoum,
Every year, most of us in USA will fill out our tax declaration and most of the time we will get tax returns. This amount of money was retained by employers to pay taxes but they may have retained more than they should, which grants us that return. The fact that this amount was saved for us during the whole year makes it (probably) some type of savings. Now, since Zakat should be paid on money we keep for a full year, should we paid the 2.5% Zakat on it?