14 CFR §250.9

1. (a)Every carrier shall furnish passengers who are denied boarding involuntarily from flights on which they hold confirmed reserved space immediately after the denied boarding occurs, a written statement explaining the terms, conditions, and limitations of denied boarding compensation, and describing the carriers' boarding priority rules and criteria. The carrier shall also furnish the statement to any person upon request at all airport ticket selling positions which are in the charge of a person employed exclusively by the carrier, or by it jointly with another person or persons, and at all boarding locations being used by the carrier.
2. (b)The statement shall read as follows:
3. (c)In addition to furnishing passengers with the carrier's written statement as specified in paragraphs (a) and (b) of this section, if the carrier orally advises involuntarily bumped passengers that they are entitled to receive free or discounted transportation as denied boarding compensation, the carrier must also orally advise the passengers of any material restrictions or conditions applicable to the free or discounted transportation and that they are entitled to choose a check instead (or cash if that option is offered by the carrier).