Anyone that is listed on the rental agreement may; obviously, drive the rental car. Most companies will permit a spouse to drive the rental car as well; whether or not the spouse is listed on the rental agreement, as long as that spouse has a valid and unexpired driver’s license.
No other persons are permitted to drive the rental car and there are no exceptions to this rule. You didn’t have time to return the car yourself, you had a medical emergency or even your own death does not make it permissible.
The rental agreement is a binding, legal document. Lawyers and insurance companies will use this legal document to their advantage. This means that if an unauthorized person is driving a rental car and is involved in a traffic accident, no insurance company is going to accept responsibility for paying for the damages to the rental car or to a third party. Not the unauthorized person’s insurance company. Not any of the authorized drivers’ insurance companies. Not even the rental car company’s insurance provider. This means that any and all authorized drivers who signed the rental agreement are legally obligated to pay for the damages to the rental car and to any third parties out of their own pockets, regardless of fault!
Additionally, many companies will assess a fine if it is discovered that an unauthorized driver has driven the rental car. This typically occurs when that unauthorized driver is the one who returns the rental car, is involved in an accident or is arrested while driving the car. Speaking of arrests, police officers have definitely been known to detain drivers that they have pulled over who are not listed on a rental agreement.
I think I have made my point. If someone else needs to drive the rental car who is not currently listed on the rental agreement as an authorized driver, stop by one of the rental car company’s offices and have them added, even if it’s just for a day. It could save you a lot of money and legal problems!