Simple Membrship plugin can only accept currencies that are support by the payment gateway that you are using.
Our plugin will work with any currency that the payment gateway supports in their API.
You can check the supported currency list (for your payment gateway) from the following section.
PayPal Payment Gateway
The following page lists the currencies that PayPal supports:
Stripe Payment Gateway
The following page has a list of currencies that Stripe supports:
Braintree Payment Gateway
The following page has a list of currencies that Braintree supports: