The only code I know of that has worked for me is MCAP01. It's generally a 20% discount with free breakfast and the booking is refundable. It's a Mastercard rate and so the online booking must be guaranteed with a Mastercard. However, I've virtually always paid on checkout with my Visa. I think it's Asia-Pacific only. I've found it can work at some of their main brands like Sofitel or Novotel but not more fringe brands. Recently, the hotels I'd used this at before haven't had the rate available. Or in 1 case it only gave a 10% discount.