The general Illinois prosecutor's statute of limitations for misdemeanor domestic battery is 18 months. Remember a prosecutor has to have enough time to conduct an investigation, too, before the running of the statute.
In some instances domestic battery can be charged as a felony, and, in that case the statute of limitations is five years.
Brinkmeier is right about the statute of limitations on a misdemeanor being 18 months from the date of the incident. He is also right that in certain instances domestic battery can be a felony. However, the statute of limitations on this felony is THREE (3) years, not five.