Legal Question in Landlord & Tenant Law in Illinois

How long ago was this? You may have blown the time period to notify them they get nothing back (the "written report"). It is unusual for a lease to demand 30 day notice of a moving date unless it is a month-to-month, so without seeing the lease it is also inappropriate to say for sure one way or the other. But from a practical standpoint, this is what I would call "some nerve". Depending on whether you wrote them already about any of this, I might just suggest writing them and saying you and they agreed to use their security deposit for last month's rent, agreed to short notice, and let things go at that. How much are we talking about? But again without seeing the lease and their demand it is inappropriate to say for sure. Remember under Illinois law if you don't follow the rules about return of security, you can be liable for 2x the amount. And the thing is that the lease may allow you to apply security to rent, or not. Normally security is not for rent, but for condition on expiration. So ultimately have a local attorney take a look at the lease, their demand, the time frame, and give you the best answer.