With Sixt Rent a Car, a spouse is not automatically included as a free additional driver in most jurisdictions. Unlike some US states where law mandates that a spouse is a permitted driver, Sixt typically requires any additional driver—including a spouse or domestic partner—to be formally added to the rental agreement at the counter and to pay a daily "Additional Driver" fee. This fee covers the extra insurance risk. Both the primary renter and the spouse must present a valid driver’s license and meet the age requirements for the specific vehicle category. However, in 2026, some corporate rates or specific loyalty tiers (such as Sixt Platinum or Diamond) may include a spouse as a free second driver as a member benefit. It is crucial to verify this at the time of booking, as allowing an unlisted spouse to drive can void your Loss Damage Waiver (LDW) or third-party liability coverage, leaving you personally responsible for the total cost of any damages or accidents that might occur during the rental period.