Authentication Request Cover Letter. The FI processes and adjudicates feeforservice claims and prior authorization requests in the PNM without being rerouted to MITS.This form is not a patient access request under 45 CFR 164.524. Mailed documents are processed within two to three business days. Some services and supplies need approval from your health plan first. This means your providers need permission to provide certain services. Providers can use the Prior Auth Check Tool, located on the Buckeye Health Plan website. Sample letter: In the letter you should mention the following: 1. To request a prior authorization, be sure to: Always verify member eligibility prior to providing services. It's also not a letter, either.