NEW YORK (AP) — Zipcar has been slapped with a $300,000 fine after U.S. regulators found that the car-sharing company allowed customers to rent vehicles with open recalls, violating federal motor safety law.

The civil penalty is a part of a consent order announced by the National Highway Traffic and Safety Administration — marking the first enforcement action against a rental car company over recalls.

Under the order, half of the $300,000 penalty is set to be paid up front — while the other $150,000 will be deferred and could become payable in the event of future violations.

In addition, the company is required to submit an audit of all Zipcar vehicles with recalls open at any time within 150 days after the consent order and provide updates to employee training materials.