The Internal Revenue Service has adopted policies that prohibit staffers who cheat on their taxes from working there, the agency's head told senators on Wednesday.

"I have no indication that anyone working for the IRS has not followed the updated procedures," IRS Commissioner John Koskinen told the Senate Finance Committee. He added that those who hired tax cheats in the past "were operating under a different set of rules and regulations."

A 2015 report by the Treasury Inspector General for Tax Administration found that 1,580 employees at the agency had willfully failed to pay their taxes, while 18,300 did so unintentionally. Of those who willfully failed, the IG found 61 percent retained their positions.

Koskinen's assurance that the IRS updated its policies to preclude less reputable employees from staying on came in response to a line of questioning from Sen. Richard Burr, R-N.C., who asked Koskinen what he should tell his voters about the issue.

"Tell your constituents that's not going to happen again," Koskinen said.