Because many counties are really hurting for revenue, some County Revenue Commissioners are going through and cleaning the books of old property tax bills. Even in good times, the Commissioners will go through periodically and round up old unpaid property tax bills. This results in some serious surprises for some taxpayers. The County Revenue Commissioners will look back multiple years (usually around 7 years) to try and collect back taxes.
The property taxes owed for a single year are generally very small in comparison to the penalties and interest accrued over time. Your bill for a single year could be 4 or 5 times (or more) higher than the original property tax bill because of accrued penalties and interest.
Some Revenue Commissioners are bad about letting interest and penalties accrue for years without notifying taxpayers. A taxpayer can end up with a huge tax bill six or seven years after the fact.
If you have paid back penalties and interest because of old property tax bills and especially if you were not notified for several years of back taxes that you owed, I suggest that you go to your local governing authority and request a refund of some or all of the penalties and interest that you paid.
You may or may not get the refund that you request but at least you would have had an opportunity to make your case before your representatives.
Good Luck.