CHICAGO (CBS)– Before the kids go out trick or treating tonight, officials recommend that parents check the Illinois Sex Offender Registry, which is available online.

Illinois law prohibits all sex offenders who committed a crime against a child from distributing candy or others items to children on Halloween, according to the Illinois Attorney General’s Office.

Sex offenders on parole, mandatory supervised release and probation may have other conditions imposed upon them to protect the public. They may be prohibited from having their porch lights on and from leaving their homes, except for verified work purposes.

You can enter your address or town on this site to get a list of registered offenders.

Illinois puts the home addresses of more than 31,000 sex offenders on a website so residents can see who lives in their neighborhoods.

However, back in May CBS 2 found that many of those addresses have not been properly undated.

How could so many slip through the cracks?

In one case, CBS 2’s Megan Hickey found a mother of young children living in a Palatine apartment building, who had no idea she had a registered sex offender as a neighbor.

That person registered with a Chicago address which doesn’t exist. In addition, he used the 60606 zip code, which is the Willis Tower.

Another sex offender who actually lives on the Northwest Side, only a few hundred feet from an elementary school, also registered with that 60606 zip. He is convicted of sexually abusing a 16-year old.

Another offender registered at 69 W. Washington St., which is the administrative building for Cook County. It’s also home to the Cook County State’s Attorney’s office. A security guard there confirmed there are no residential properties at that address.

A spokesperson for the Cook County Sheriff’s Office says addresses in their jurisdiction — unincorporated Cook County and the Village of Ford Heights — are physically checked to make sure offenders are in compliance. Registered sex offenders also come to the Sheriff’s Police Department annually on Halloween to update their information.

A spokesperson for the Illinois Department of Corrections also said if the offender has been discharged from IDOC custody, it is the responsibility of local law enforcement to verify the address. The Parole Office verifies the addresses for those on supervision.