The first step in using an ACH authorization form is to request this form from your bank or financial institution. There are three primary ways to fill out an ACH authorization form: paper, phone, or online.Our company has a standard letter that outlines our banking information to be used for ACH. Can you accept this letter instead of completing an enrollment form? 1) The ACH Form must be filled out completely. 2) A voided check must be attached. This guide explains why ACH authorization forms are so important and provides templates for businesses wishing to utilize ACH payments. If I change banks or accounts, I acknowledge that I must allow one month after I notify my department's payroll representative in writing. Trying to fill out a government form and its asking for my ACH (Automated Clearing house) contact info but I have no clue how to get that. Houston animal clinic.