I am not familiar with Michigan law, but USUALLY, due process requires that papers be served by someone who is NOT a party to the case (or related to a party).
Since you are the plaintiff, it is unlikely that you can legally "serve" the garnishment.
You should find a local "attorney service" that handles service of process for attorneys and hire them to serve the garnishment for you. They will get it right and it will not cost much.
If you need further clarity, please email me at MICHAEL@MIRELAND.US Answers to questions are for general information purposes only and do not establish an attorney-client relationship. This is not legal advice, simply information. You SHOULD NOT act on this information without consulting a competent bankruptcy attorney in your area and providing ALL relevant information.
A State of Michigan tax garnishment is usually served in October for the coming tax filing. You are running the risk that someone else who has a judgment against your defendant may have filed a tax garnishment ahead of you, and you will likely collect nothing. If you have already filed it with the court, you can mail the copy to the State via certified mail, return receipt requested, so you know they received it. Use the address on the official form and make sure it has the defendant's SS # on it. The return copy can act as your "proof of service' and can be completed on the back, stating how and when you served the State and the defendant. The defendant can be served by mail.