That on-again, off-again Booking Holdings introduction of charging hotels commissions on their resort fees or other extra charges quietly is underway - mostly outside the United States.

Booking Holdings spokesperson Leslie Cafferty confirmed Monday that the company began charging hotels commissions on mandatory extra/hidden fees - those excluded from the room rate - including resort fees and parking fees, for example, around the world except for some properties in the United States.

Related: Hotels face growing backlash against resort fees