Supplemental pleadings showing matters arising since the original pleading may be filed in actions for equitable relief by either party. In any action for legal or equitable relief, any defendant may file counterclaims against any plaintiff and cross claims against any codefendant provided that each such counterclaim and cross claim arises out of the transaction or one of the transactions which is the subject of the plaintiff’s complaint; and if necessary, additional parties may be summoned in to answer any such counterclaim or cross claim. A defendant may also file a counterclaim or cross claim under this section against any other party to the action for the purpose of establishing that party’s liability to the defendant for all or part of the plaintiff’s claim against that defendant.
Section 10-10.Supplemental Pleadings; Counterclaims
Current through August 12, 2025 (2026 Practice Book edition) · Last verified July 9, 2026
In one sentenceThis section allows supplemental pleadings for events arising after the original pleading in equitable actions, and lets a defendant file counterclaims or cross claims arising from the same transaction as the plaintiff's complaint.
Full Text of Section 10-10
Amendment History
(P.B. 1978-1997, Sec. 116.)
Plain-English Summary
Section 10-10 covers two related tools. First, in actions for equitable relief, either party may file a supplemental pleading to bring in matters that arose after the original pleading was filed. Second, in any action for legal or equitable relief, a defendant may file a counterclaim against the plaintiff or a cross claim against a codefendant, so long as the claim arises out of the transaction (or one of the transactions) that is the subject of the plaintiff’s complaint. If needed, the defendant can summon in additional parties to answer the counterclaim or cross claim.
A defendant may also use a counterclaim or cross claim under this section for a narrower purpose: to establish that another party to the action is liable to the defendant for all or part of what the defendant may owe the plaintiff.
Frequently Asked Questions
What is a supplemental pleading under Section 10-10?
It is a pleading that brings in matters arising after the original pleading was filed, and it is available to either party in actions for equitable relief.
Can a defendant file a counterclaim against a codefendant?
Yes, Section 10-10 lets a defendant file a cross claim against a codefendant, provided it arises out of the transaction that is the subject of the plaintiff's complaint.
Do counterclaims under this section have to relate to the plaintiff's claim?
Yes. Each counterclaim or cross claim must arise out of the transaction, or one of the transactions, that is the subject of the plaintiff's complaint.
Can new parties be added to answer a counterclaim?
Yes, the section allows additional parties to be summoned in when necessary to answer a counterclaim or cross claim.
Source & verification. The section text is reproduced verbatim from the
official Connecticut Practice Book (Conn. Practice Book § 10-10). Prescribed by the Judges of the Superior Court of Connecticut (Conn. Gen. Stat. Section 51-14). The plain-English summary is original and written by us. Last verified July 9, 2026. ·
Official source
Also known as: Connecticut counterclaim rulecross claim against codefendant CTsupplemental pleading equitable reliefcounterclaim same transaction requirementadding parties to answer counterclaim