A Letter of Authorization (LOA) must contain the following information: Letter must be on company letterhead. This Authorization Letter sample is available for use on UpCounsel.The sole purpose of this form is to authorize the above named representative to complete the transaction indicated. Add necessary details, such as your position regarding the duties you delegate. For an example of content to include, see the sample letter of authorization. Authorization to Complete Blank Check Amount. MV-507. One of the tips for writing an authorization letter for sample of authorization letter claiming documents is to be very specific and detailed. Are you thinking about getting Authorization Letter to fill?