I have a judgement on someone and was wanting to know if I can garnish they taxes.

No you cannot. You can, though, garnish wages or a bank account... or get a lien on their property if they have any.

Actually, it IS possible to garnish the tax refund, but it requires approval through the federal court system; it is both complicated and time-consuming; and it can be easliy defeated once the person who is the target of the garnishment is made aware of it.

For these reasons, I would not bother.