If this was a service charge based upon the use of a debit card, that was improper as I believe only certain government agencies are permitted to charge a service charge. The fact that the s.c. was handwritten also raises concern. I hope the asker disputed this with the management . The charge can also be disputed with the debit card company. If it was truly a gratuity, that is usually reserved - with prior notice - for application to larger parties. Hopefully this was not the server dong something underhanded.
There is a legal distinction between a "service charge" and a gratuity. I think the charge you are describing would constitute a "service charge." Possibly, someone at the Illinois Restaurant Association may be able to answer your question about the specifics of a restaurant's adding a service charge to a diner's check in Illinois.
Illinois Restaurant Association
33 W. Monroe, Suite 250
Chicago, IL 60603
Phone: (312) 787-4000
Toll Free: (800) 572-1086
Not legal advice, just my two cents. I don't practice law in Illinois or hold Illinois licensure. If you need legal advice, please consult a lawyer who does.
I concur. If you are not successful there, you might want to meet with the Manager of the venue informally to see if you can get it taken off. If this still doesn't work you might consider suing the restaurant in Small Claims Court. Good Luck!
I think your first step is to take this to the manager of the Restaurant to determine if the waiter/waitress was cheating you by adding an unauthorized tip or if it was a routine service charge such as for a pickup order. If you receive no satisfaction from the manager and it is a chain restaurant, get the name of the regional manager and escalate it. They will generally issue you a credit thinking that if you went that far with it, you must be upset enough that they will lose your future business if they do not resolve it.
I am not your lawyer and you are not my client. Free advice here is without recourse and any reliance thereupon is at your sole risk. This is done without compensation as a free public service. I am licensed in IL, MO, TX and I am a Reg. Pat. Atty. so advice in any other jurisdiction is strictly general advice and should be confirmed with an attorney licensed in that jurisdiction.