The California board that processes tax returns says it issued 23,500 refunds without verifying whether people had entered accurate wage information.
The Franchise Tax Board will begin notifying people on Monday if they owe more to the government than they paid or if a bigger refund check is coming. Most people in that pool will see no changes to their returns at all, said Denise Azimi, spokeswoman for the board.
The error occurred over three days in March because of a technology glitch that has been fixed, she said. The glitch allowed the returns to be sent before the state could verify that people had reported their withholdings correctly. Anyone who entered their information correctly should see no change.
Azimi could not provide an exact number of incorrect returns.
The error didn't reveal other vulnerabilities in the state's system. Only returns filed between March 8 and March 11 were affected.
The board announced the error on its website Tuesday.