Do you need a accident report if you total your car?

I am a lawyer in CT and practice in this area of the law.  There is no requirement that a police report is made under the law.  I suggest that your nephew report the incident to his insurance carrier if he was at fault as he may be able to be paid for the value of the car as of the date he totaled it.  If someone else is at fault, then he should hire a lawyer to seek compensation absent his ability to resolve it himself with the at fault driver's insurance company.

Each driver involved in an Illinois traffic accident must file a crash report if the accident caused a death, bodily injury, or more than $1,500 of property damage.

Many Illinois towns require law enforcement to work every accident, but if a police officer does not appear on the scene, you need to file a report with the local police department, sheriff's office, or Illinois State Police as soon as possible. If you aren't able to file the report due to injury, and you had a passenger, the passenger may file the report for you.

You must also file a report with the Illinois Department of Transportation no later than 10 days after the accident. You may pick up the required forms from a local insurance agent or law enforcement office.

If you're involved in an accident that meets the crash reporting requirements but you fail to file a report, you could be hit with a $2,500 fine or up to a year in jail.  If you're involved in an accident and leave the scene, then you're considered a hit-and-run driver―and the penalties become much more severe.

There's a 30-minute window where you can report the accident and face only the penalties above, if you left the scene. If you leave the scene and more than 30 minutes elapse without you reporting the accident, however, then you face a $25,000 fine, up to three years in jail, the suspension of your driver's license if property damage is more than $1,000, and revocation of your license if the accident resulted in an injury or death.