Pennsylvania Code
Title 231 - RULES OF CIVIL PROCEDURE
Part I - GENERAL
Chapter 1000 - ACTIONS
Subchapter A - CIVIL ACTION
PLEADINGS
Rule 1033 - Amendment

(a) A party, either by filed consent of the adverse party or by leave of court, may at any time change the form of action, add a person as a party, correct the name of a party, or otherwise amend the pleading. The amended pleading may aver transactions or occurrences which have happened before or after the filing of the original pleading, even though they give rise to a new cause of action or defense. An amendment may be made to conform the pleading to the evidence offered or admitted.

(b) An amendment correcting the name of a party against whom a claim has been asserted in the original pleading relates back to the date of the commencement of the action if, within 90 days after the period provided by law for commencing the action, the party received notice of the institution of the action such that it will not be prejudiced in maintaining a defense on the merits and the party knew or should have known that the action would have been brought against the party but for a mistake concerning the identity of the proper party.

(c) An amendment substituting the actual name of a defendant for a Doe designation as provided in Rule 2005 relates back to the date of the commencement of the action if, within the time provided by Rule 401 for service, the defendant named by the amendment has received actual or constructive notice of the commencement of the action such that it will not be prejudiced in maintaining a defense on the merits and the defendant knew or should have known that the action would have been brought against it but for lack of knowledge of the defendant's actual name.