Amex Membership Rewards → Marriott Bonvoy: 20% transfer bonus

American Express is running a 20% bonus on Membership Rewards transfers to Marriott Bonvoy through September 25, the first bump on this pairing in several months.

Marriott's category-based chart requires far more points per night than competing hotel programs, so a redemption only clears 1 cent per point at the higher categories — the transfer bonus is what pushes many stays into decent value territory.

Best used for a specific booked stay rather than speculative points hoarding: check the cash rate first, and only transfer if the bonus-adjusted points price beats it.