By DAVID SEIFMAN

The city's Finance Department made a monumental blunder in the property-tax rolls, mistakenly boosting market values on some co-ops by as much as 147 percent, The Post has learned.

The whopping error then left the department scrambling to reduce the values of the 139 affected co-ops -- mostly in Queens -- by more than $300 million.

Officials blame a computer error for providing incorrect data to assessors, who then used the numbers to set the values on the units.

"There was a glitch," admitted Finance Department spokesman Owen Stone.

The increased values were for the upcoming year, and no resident overpaid in taxes.

Spotted here