If law enforcement is called to the crash, then law enforcement may complete the report. If law enforcement does not file the report, you will need to complete the Wisconsin Driver Report of Crash DT4002.
Per Wisconsin Statute s.346.70(1), any crash within the State of Wisconsin must be reported when it results in:
-Injury of a person
-$1,000 or more damage to any person's vehicle or property
-Damage of $200 or more to state or other government-owned property other than a vehicle
If you received a letter from the Department of Transportation stating you were involved in a reportable crash and requesting you to complete a report, you must complete a crash report https://wisconsindot.gov/Pages/safety/crsh-rpt/default.aspx