31 CFR § 19.820 - How much time do I have to contest a proposed debarment?
(a) As a respondent you or your representative must either send, or make arrangements to appear and present, the information and argument to the debarring official within 30 days after you receive the Notice of Proposed Debarment.
(1) When delivered, if we mail the notice to the last known street address, or five days after we send it if the letter is undeliverable;
(2) When sent, if we send the notice by facsimile or five days after we send it if the facsimile is undeliverable; or
(3) When delivered, if we send the notice by e-mail or five days after we send it if the e-mail is undeliverable.