AURORA, Colo. -- Condo owners living in an area north of Southlands Mall said they were shocked to learn they were part of a special taxing district called Sorrel Ranch Metropolitan District.

The assessor's office never entered the development into the system so the owners say they didn't know they owed extra property taxes.

Many of them are now faced with a steep bill, during the holidays, at a time when the economy is already making money tight.

"It's their fault, not our fault," said resident Michael Done.

Done said he was shocked to learn he owed more money because he said he had been paying things like property taxes for the school district since he moved in.

"I was paying about $800 per year for the taxes and now they are asking for another $800?," said Done.

Arapahoe County treasurer Doug Milliken said it is an "unfortunate" situation but Colorado law has tied their hands. It is the county's responsibility to collect taxes for the Sorrel Ranch Metro District.

However, the county cannot collect five years worth of taxes, which is owed. The law only lets them collect the last two years.

When 7NEWS asked Milliken who was to blame for the "clerical error", Milliken said that still wasn't clear.

Condo owners have until the end of the month to pay the bill without incurring late fees. If they pay after the deadline, they will be assessed a 4 percent penalty.