The Official Website for the Commonwealth of Pennsylvania. Secretary's Letters are not intended as and do not constitute legal advice.(2) A letter of reference from a bank. (3) Three letters of reference from reputable business concerns. In order to make a bank authorization letter, it's important to empower someone with bank relates issues, for example in taking collecting or sign on documents. Number of signatures required . Execute other agreements that Financial Institution may require, and perform or cause to be performed any further action. If you need to show someone your bank balance, you simply give them a copy of your last bank statement. If the department approves the application, it shall issue to the institution a letter of authority to establish the branch. Bank letterhead; Account number; Routing number; Business name.