Rule 64 — Intervention

(a) Intervention of Right:

(1) In General: On timely motion, the Court must permit anyone to intervene who is given an unconditional right to intervene by a Federal statute.

(2) Existing Rules: For the requirements relating to intervention in certain actions, see Rules 216, 225, 245, and 325(b).

(b) Permissive Intervention:

(1) In General: On timely motion, the Court may permit anyone to intervene who:

(A) is given a conditional right to intervene by a Federal statute; or

(B) has a stake in the outcome of the litigation before the Court that may not be adequately protected by the existing parties, if the Court determines in its discretion that permitting the intervention (i) may contribute to a more complete presentation of the legal issues to be decided and

(ii) is in the interest of justice.

(2) By a Government Officer or Agency: On timely motion, the Court may permit a Federal or State governmental officer or agency to intervene if a party’s claim or defense is based on:

(A) a statute or executive order administered by the officer or agency; or

(B) any regulation, order, requirement, or agreement issued or made under the statute or executive order.

(3) Delay or Prejudice: In exercising its discretion, the Court must consider whether the intervention will unduly delay or prejudice the adjudication of the issues raised by the existing parties.

(c) Notice Required: A motion to intervene must be served on the parties as provided in Rule 21 and must comply with the requirements of Rules 50 and 54. The motion must state the grounds for intervention and the reasons why intervention should be permitted.

(d) Intervenor’s Role: The Court, in its discretion, will determine the extent to which an intervenor may participate in the proceedings.

(As adopted, effective March 20, 2023, 160 T.C. 609–12.)