When purchasing a subscription plan the service generates an invoice. This invoice can be paid via Check or Credit Card. The following is a sample invoice generated for our of our test accounts.
Once payment is completed the invoice switches to Paid and you are licensed to use the service.
It is important to note that we do not store or receive any credit card or financial information in our service. Stripe is the company that handles our transactions and their 'checkout" product allows us to process payment without ever transferring sensitive or PII data to us. You can read more about their security features on their help site.
Once we receive notification we will note this in your account and credit it once the check has cleared.