ACH transfers are made via your Stripe account in connection with Plaid.com as it verifies your client’s bank account and provides instant verification of their accounts. Stripe is a reputed technology company that specializes in online payments and billing. You can read about the company, its Services Agreement and Security Policy here. The authorization is just for the current invoice and not for any future payments. So, your clients are required to add and log in to their accounts again the next time they use the ACH ePayments link.