Good evening, @schmidtfs. 

It's great to see you back in the Community. I'd be more than happy to give you some information on if our QuickBooks Online processor accepts AMEX. 

Yes, we do accept American Express with QuickBooks Payments. Review this guide to find out more details about QuickBooks Payments. 

Check out this link that could help you in the future as well: Add or remove AMEX credit card processing for QB Payments account. 

This should answer your question. Don't hesitate to reach back out if you need any more assistance. Take care!