The sole purpose of this form is to authorize the above named representative to complete the transaction indicated. Please complete this printable form online or write legibly in blue or black ink ONLY, within the lines provided.A Letter of Authorization (LOA) must contain the following information: Letter must be on company letterhead. This authorization letter allows a representative to transfer ownership of a vehicle on behalf of the lawful owner. Edit, sign, and share authorization letter harris county online. No need to install software, just go to DocHub, and sign up instantly and for free. The MV 454 form is an authorization letter that allows a designated representative to carry out specific transactions related to vehicle registration. Edit, sign, and share authorization letter harris county online. No need to install software, just go to DocHub, and sign up instantly and for free. For titling purposes (for example, letters testamentary, letters of administration or TxDMV Forms VTR-122, Rights of Survivorship Ownership Agreement or.