an ach debit authorization is consent given by a customer for a business to collect future payments from them. before a business can begin collecting ach debit payments from a customer, they must receive an ach debit authorization from them. this authorization is required for a business to collect ach payments and should include the amount and frequency to be debited. explain to the customer how they can revoke their authorization, including the required notice period (which minimizes the chances of a misunderstanding) by paper – customers can complete paper authorization forms and return them to you. over the phone – you can take your customer’s details over the phone, but must provide additional information when taking these details  (more on this below). as noted above, ach authorization forms don’t have a standard format or layout, but must contain several key elements. in this context, an existing relationship means either having a written agreement in place, or the customer has purchased goods or services from you in the last two years.