Wash. Super. Ct. Civ. R. 13

(a) Compulsory Counterclaims. A pleading shall state as a counterclaim any claim which

at the time of serving the pleading the pleader has against any opposing party, if it arises out of

the transaction or occurrence that is the subject matter of the opposing party's claim and does not

require for its adjudication the presence of third parties of whom the court cannot acquire

jurisdiction. But the pleader need not state the claim if

(1) at the time the action was commenced the claim was the subject of another pending

action, or

(2) the opposing party brought suit upon the pleader’s claim by attachment or other process

by which the court did not acquire jurisdiction to render a personal judgment on that claim, and

the pleader is not stating any counterclaim under this rule.

(b) Permissive Counterclaims. A pleading may state as a counterclaim any claim against

an opposing party not arising out of the transaction or occurrence that is the subject matter of the

opposing party's claim.

(c) Counterclaim Exceeding Opposing Claim. A counterclaim may or may not diminish

or defeat the recovery sought by the opposing party. It may claim relief exceeding in amount or

different in kind from that sought in the pleading of the opposing party.

(d) Counterclaim Against the State. These rules shall not be construed to enlarge beyond

the limits now fixed by law the right to assert counterclaims, or to claim credits against the State

or an officer or agency thereof.

(e) Counterclaim Maturing or Acquired After Pleading. A claim which either matured

or was acquired by the pleader after serving the pleading may, with the permission of the court,

be presented as a counterclaim by supplemental pleading.

(f) Omitted Counterclaim. When a pleader fails to set up a counterclaim through

oversight, inadvertence, or excusable neglect, or when justice requires, the pleader may by leave

of court set up the counterclaim by amendment.

(g) Cross Claim Against Coparty. A pleading may state as a cross claim any claim by

one party against a coparty arising out of the transaction or occurrence that is the subject matter

either of the original action or of a counterclaim therein or relating to any property that is the

subject matter of the original action. Such cross claim may include a claim that the party against

whom it is asserted is or may be liable to the cross claimant for all or part of a claim asserted in

the action against the cross claimant.

(h) Joinder of Additional Parties. Persons other than those made parties to the original

action may be made parties to a counterclaim or cross claim in accordance with the provisions of

rules 19 and 20.

(i) Separate Trials; Separate Judgment. If the court orders separate trials as provided in

rule 42(b), judgment on a counterclaim or cross claim may be rendered in accordance with the

terms of rule 54(b), even if the claims of the opposing party have been dismissed or otherwise

disposed of.

(j) Setoff Against Assignee. The defendant in a civil action upon a contract express or

implied, other than upon a negotiable promissory note or bill of exchange, negotiated in good

faith and without notice before due, which has been assigned to the plaintiff, may set off a

demand of a like nature existing against the person to whom the defendant was originally liable,

or any assignee prior to the plaintiff, of such contract, provided such demand existed at the time

of the assignment thereof, and belonging to the defendant in good faith, before notice of such

assignment, and was such a demand as might have been set off against such person to whom the

defendant was originally liable, or such assignee while the contract belonged to defendant.

(k) Other Setoff Rules. [Reserved. See RCW 4.32.120 through 4.32.150 and

RCW 4.56.050 through 4.56.075.]