Most likely leftover from before the LTR would have taken hold. No Bills means your sim shouldn't receive more bills/continue to be charged for things like property taxes from that point forward, not that they are exempt from paying the prior ones. But you can tempt fate if you like and see if the friendly Repo Sim shows up as scheduled.
I did this once when my sim had an unpaid bill for §2 on an essentially empty lot. It was really funny when the Repo Sim showed up and looked all confused because there was nothing to take except a mailbox, municipal trash can, old newspapers strewn about, and some weeds. He shook his fist and said he would be back some day (or something like that). My sims were busy sleeping at the firehouse at the time. :)