More than a half million parking tickets — totaling about $26 million — have been either refunded or dismissed by the city after it discovered a technical error.

The Department of Finance discovered a change in city rules for failing to display a muni meter receipt or an expired muni meter receipt, a spokeswoman said Monday. Some tickets didn’t apply the rule and the drivers were unnecessarily fined.

As a result, the department sent two sets of letters to about 500,000 people who received the tickets, informing them about the error.

There are about 400,000 refunds totaling approximately $18 million and 106,808 dismissals totaling roughly $8 million, the spokeswoman said in a statement.

1010 WINS first reported the refunds and dismissals Monday afternoon.