They give you a seven day grace period to pay them online at illinoistollway.com. No need to pull over to pay the tolls, just hop on-line within seven days, look up your license plate number, and pay it. What is the fine if you don't pay it? They send mail to owner of car to pay it and charge approx $5. If you don't pay that in about a month you get another $40 fine or so. After that if it isn't in your state I have heard they can't do a whole lot. However, if it is in the state you are from I hmthink they can do something with car registration/your license. I also heard something about effecting your credit, but not sure about that either. I gotta be honest though I know a lot of people who whip through tolls and never get anything in the mail.