Charleston County property owners who have not paid their 2012 property tax bills have until Friday to pay up, before the properties go to the auction block in a delinquent tax sale that begins Dec. 9.

Once a property goes through the annual delinquent tax sale, the owner still has a year to reclaim it, but at great expense. A tax bill amounting to hundreds of dollars can turn into thousands of dollars in redemption costs if a property is sold and later reclaimed.

There were more than 2,200 properties, plus hundreds of mobile homes, listed for the Charleston County delinquent tax sale as of Monday. Typically, many property owners with overdue bills pay them before the deadline.

Delinquent tax sales in Berkeley and Dorchester counties were held in November.

In 2010, amid the worst of the real estate meltdown, Charleston County sold 1,299 properties and 507 mobile homes at the delinquent tax sale. In years when the economy was better, the county sold fewer than 500 properties.

At delinquent tax sales, investors and speculators bid on properties primarily to receive outsized interest payments. A person whose property is sold due to delinquent property taxes must pay up to 12 percent interest on the bid amount, plus the taxes, penalties and costs, in order to reclaim it.

Most bidders end up collecting the interest payments, but between 10 percent and 20 percent of the properties are usually not reclaimed, and in those cases the bidders get title to the property after a year has passed.

If the amount bid was higher than what was owed in taxes — and it usually is — then the difference is supposed to go back to the prior owner of the property, if the property is not reclaimed. In some cases the prior owners can’t be located or the ownership can’t be sorted out, and in those cases the county government ends up keeping the excess funds.

To prevent a property from being sold at auction next week, payments must be received at the Charleston County Treasurer’s Office by 5 p.m. Friday. Payments must be made with cash or certified funds.

Reach David Slade at 937-5552