Sign up for our daily newsletterEmail addressSign upI would like to subscribe to The Points Guy newsletters and special email promotions. The Points Guy will not share or sell your email. See privacy policy.Update: Some offers mentioned below are no longer available. View the current offers here.Using your The Business Platinum Card from American Express OPEN card for big purchases just got a lot more valuable. For a limited time, using this card will net you 50% more points on transactions of $5,000 or more, such as a new car or even a $170 million painting. Obviously most people won’t be using this perk too often, but it’s a fantastic chance to boost your earnings if you’re making a large purchase. For smaller items, you could also use the Amex Everyday Preferred card, which offers a similar bonus if you make 30 or more purchases on the card within a billing period. Note that this promotion offer was sent via email, so it’s possible that this is a targeted opportunity.You can get a bonus on big purchases by using your Amex Business Platinum card.We already value Amex Membership Rewards points at 1.9 cents per point, so with this bonus you’re getting even better value. The current offer will be available through the end of April, so there’s plenty of time to plan for purchases, although you can only earn a total of 50,000 additional points.