Rule 15.Amended and Supplemental Pleadings

Rule 15 is identical to its civil counterpart, and the source says so in a line of its own before subsection (a).

Amending once, and afterwards

A party may amend once as a matter of course at any time before a responsive pleading is served and before entry of an order of dismissal. Where the pleading is one to which no responsive pleading is permitted and the action has not been placed on the trial calendar, the party may amend within 20 days after service. Otherwise amendment requires leave of court or the adverse party's written consent — and leave shall be freely given when justice so requires.

The response deadline after an amendment is the longer of the time remaining to respond to the original pleading or 10 days after service of the amended pleading, unless the court orders otherwise.

Conforming to the evidence

Subsection (b) covers the trial situation. Issues tried by express or implied consent are treated in all respects as if they had been raised in the pleadings, and the pleadings may be amended to conform on motion at any time, even after judgment — with failure to amend not affecting the result. Where evidence is objected to as outside the issues, the court may allow amendment and shall do so freely when it will serve the presentation of the merits and the objecting party fails to satisfy the court that admitting the evidence would prejudice the maintenance of its action or defense on the merits. A continuance may be granted to let the objecting party meet the evidence.

Relation back, and supplemental pleadings

Subsection (c) is short and broad: whenever the claim or defense in the amended pleading arose out of the conduct, transaction or occurrence set forth or attempted to be set forth in the original pleading, the amendment relates back — including an amendment changing a party. The Massachusetts rule states that without the conditions the federal rule attaches.

Subsection (d) allows a supplemental pleading, on motion and reasonable notice, setting out transactions, occurrences or events that have happened since the date of the pleading being supplemented. Permission may be granted even though the original pleading is defective in stating a claim or defense. The court may order the adverse party to plead to it, specifying the time.

Rule 15 has a second job worth noting: Rule 12(h)(1) preserves the waivable defenses if they are included in an amendment permitted by Rule 15(a) to be made as a matter of course.