Update
Stripe, the integrated provider for NationBuilder’s payment processor, has updated its American Express rate for nonprofits in the United States and Canada to a flat fee of 3.5% compared to the previous rate of 2.2% + $0.30. This will not affect any other donations and the NPO rate of 2.2% + $0.30 will still be applied to the transactions processed on other credit card providers. You can get more information on the international and domestic rates that may apply here.