49 C.F.R. § 89.43
(a) Notification by debtor. A debtor who receives a Notice of Intent may present, for 60 days from the date of the Notice of Intent, information that all or part of the debt is not past-due or legally enforceable. (However, this does not extend the regulatory period for submitting written statements or for requesting an administrative hearing on the merits of an alleged violation, nor does it extend the period to appeal an assessed civil penalty.) To comply with this procedure, the debtor must: