24 C.F.R. § 180.500 – Discovery.

(a) In general. This subpart governs discovery in aid of administrative proceedings under this part. Discovery in Fair Housing Act matters shall be completed 15 days before the date scheduled for hearing or at such time as the ALJ shall direct. Discovery in non-Fair Housing Act matters shall be completed as the ALJ directs.
(b) Scope. The parties are encouraged to engage in voluntary discovery procedures. Discovery shall be conducted as expeditiously and inexpensively as possible, consistent with the needs of all parties to obtain relevant evidence. Unless otherwise ordered by the ALJ, the parties may obtain discovery regarding any matter, not privileged, that is relevant to the subject matter involved in the proceeding, including the existence, description, nature, custody, condition, and location of documents or persons having knowledge of any discoverable matter. It is not grounds for objection that information sought will be inadmissible if the information appears reasonably calculated to lead to the discovery of admissible evidence.
(c) Methods. Parties may obtain discovery by one or more of the following methods:
1. (1) Deposition upon oral examination or written questions.
2. (2) Written interrogatories.
3. (3) Requests for the production of documents or other evidence for inspection and other purposes.
4. (4) Requests for admissions.
5. (5) Upon motion of a party, the presiding ALJ may issue an order requiring a physical or mental examination of a party or of a person in the custody or under the legal control of a party.
(d) Frequency and sequence. Unless otherwise ordered by the ALJ or restricted by this subpart, the frequency or sequence of these methods is not limited.
(e) Non-intervening aggrieved person. For purposes of obtaining discovery from a non-intervening aggrieved person, the term party as used in this subpart includes the aggrieved person.