Contractors overcharged the city for nearly $1.3 million last year, sometimes sending bills for work that was never done, according to a new report from City Controller Alan Butkovitz.

Butkovitz said the city did not pay the overcharges because they were caught by a pre-audit team in his office, which approached the contractors and corrected the mistakes.

In a statement Butkovitz said the team "keeps a very close watch on the city's construction projects."

More than $272,000 of the $1.3 million was charged by a contractor working on asbestos-remediation projects, Butkovitz said. An additional $86,000 was for work by one contractor at City Hall that was never performed, including new grooved concrete for the apron around the building, Butkovitz said.

Butkovitz said just over half of the overbilling was on contracts at the Philadelphia International Airport, including contractors charging rates that were too high. An additional 45 percent of the overbilling was through the Department of Public Property, 3 percent through the Water Department, and less than 1 percent through the Streets Department.

Butkovitz said his office has held workshops for city employees in hopes of helping them identify areas where contractors are overbilling.