Intent-to-Audit letter
In short
The letter that officially begins an audit. It arrives after the auditor has already made contact, and that earlier contact is what closes the voluntary disclosure door.
In full
The Intent to Audit Letter formally opens an audit. ADOR's sequence is that an auditor receiving the assignment contacts the taxpayer, a mutually agreed time for an opening interview is set, and the letter is then sent together with an opening interview confirmation letter to officially begin the audit.
The order matters more than the letter does. By the time the letter arrives, contact has already been made, and contact is the event that ends eligibility for the Voluntary Disclosure Program. ADOR states that a taxpayer is only eligible to apply if the Department has not already made contact regarding an audit, a non-filer notice or an enforcement investigation.
So a contractor weighing whether to come forward is not weighing it against the letter. The decision closes at the first call.
The letter itself is procedural. It confirms that an audit has begun, and the examination of records follows from there.
ADOR TPT Audit; ADOR Disclosure and Compliance Programs