This most commonly happens if you refinanced, or in any way changed the information on your tax bill. First, do not worry. Your tax agent knows they owe the taxes and will usually pay them anyway. To correct the mailing of the bill, ask your bank or lender to request in writing a change of mailing from the Treasurer's Office. This must be in writing to conform to the law. 

If your taxes become delinquent more than a year, the Treasurer will file with the County Prosecuter's Office to sell the property at Sheriff's auction.