RULE 10
Amended and Supplemental Pleadings

Section 1. Amendments in general. — Pleadings may be amended by adding or striking out an allegation or the name of any party, or by correcting a mistake in the name of a party or a mistaken or inadequate allegation or description in any other respect, so that the actual merits of the controversy may speedily be determined, without regard to technicalities, and in the most expeditious and inexpensive manner. 

Section 2. Amendments as a matter of right. — A party may amend his pleading once as a matter of right at any time before a responsive pleading is served or, in the case of a reply, at any time within ten (10) days after it is served. 

Section 3. Amendments by leave of court. — Except as provided in the next preceding section, substantial amendments may be made only upon leave of court. But such leave may be refused if it appears to the court that the motion was made with intent to delay. Orders of the court upon the matters provided in this section shall be made upon motion filed in court, and after notice to the adverse party, and an opportunity to be heard. 

Section 4. Formal amendments. — A defect in the designation of the parties and other clearly clerical or typographical errors may be summarily corrected by the court at any stage of the action, at its initiative or on motion, provided no prejudice is caused thereby to the adverse party. 

Section 5. Amendment to conform to or authorize presentation of evidence. — When issues not raised by the pleadings are tried with the express or implied consent of the parties they shall be treated in all respects as if they had been raised in the pleadings. Such amendment of the pleadings as may be necessary to cause them to conform to the evidence and to raise these issues may be made upon motion of any party at any time, even after judgment; but failure to amend does not effect the result of the trial of these issues. If evidence is objected to at the trial on the ground that it is not within the issues made by the pleadings, the court may allow the pleadings to be amended and shall do so with liberality if the presentation of the merits of the action and the ends of substantial justice will be subserved thereby. The court may grant a continuance to enable the amendment to be made. 

Section 6. Supplemental pleadings. — Upon motion of a party the court may, upon reasonable notice and upon such terms as are just, permit him to serve a supplemental pleading setting forth transactions, occurrences or events which have happened since the date of the pleading sought to be supplemented. The adverse party may plead thereto within ten (10) days from notice of the order admitting the supplemental pleading. 

Section 7. Filing of amended pleadings. — When any pleading is amended, a new copy of the entire pleading, incorporating the amendments, which shall be indicated by appropriate marks, shall be filed. 

Section 8. Effect of amended pleadings. — An amended pleading supersedes the pleading that it amends. However, admissions in superseded pleadings may be received in evidence against the pleader, and claims or defenses alleged therein not incorporated in the amended pleading shall be deemed waived. (Rules of Court)

Read:

May a complaint be amended to cure a failure to state a cause of action?
May amendment be allowed to correct a jurisdictional defect?
Is there a need to serve new summons after a complaint is amended?