When creating a subscription, you have the ability to select either Automatically charge payment method or Notify client to pay manually. The payment method displayed is the client’s primary payment method. You can change the payment method for the client if they have multiple payment methods added to their account.
Note: You can add a payment method for a client manually here, but this only applies to credit card payments. For ACH payments, the client must complete the steps themselves to connect their bank account. It is not possible for internal users to manually add an ACH payment method for a client.
If you want to only accept ACH payments, you can click on Advanced Settings when creating the subscription and ensure that only the Allow Payment via ACH option is turned on. Alternatively, you can choose to only accept credit card payments in the same manner.