On January 1st, 2017 American Express are making changes to the way late fees are handled on charge cards (via Frequent Miler). Previously you had until the next statement closing date to pay your bill to avoid any late fees with American Express on their charge cards. On January 1st, 2017 you will need to pay your bill before the payment due date shown on your statement – otherwise you will pay a late fee.
Keep in mind that this only affects American Express charge cards (these differ from credit cards in that you can’t carry a balance on a charge card – although that isn’t even technically true as you can enroll in pay over time now on charge cards). This is likely a revenue generation tool by American Express, I’m not entirely sure why they don’t do away with charge cards entirely given the fact that are so eager to earn interest revenue from customers (the whole reason they have pay over time on charge cards). A better idea would be to issue credit cards with flexible spending limits instead.
