Hi urbanmopservices,
It's great to hear that you're using QuickBooks Online Payments to ensure your customers pay on time. Providing them with the 'pay now' option on the invoices they receive is a valuable time saver. However, at this time, the option to include AMEX to the list of accepted payment methods, is not available in Canada. Payments can only be received in Canadian currency, even if American-sourced credit cards have Canadian details. To learn more about the accepted payment methods, click here.
If you have any other questions, feel free to reach back out. We'd be happy to help!