Cook County back taxes/forfeited taxes resolved during closing?

[Davis C.]

If there is a property with several years of open back taxes, with a few years forfeited (offered at sale but not purchased), do they need to be paid off before closing?

Or can it be handed like normal, with the debt prorated and credited to the buyer? I assume that would be ok, but since the penalties keep adding up every month, it would add complications.