Del. Fam. Ct. R. Civ. P. 15
(a) Amendments. A party may amend the party's pleading once as a matter of course at any time before a responsive pleading is served or, if the pleading is one to which no responsive pleading is required or permitted and the action has not been placed upon the trial calendar, that party may so amend it at any time within 20 days after it is served. Otherwise a party may amend the party's pleading only by leave of Court or by written consent of the adverse party; and leave shall be freely given when justice so requires. A party shall plead in response to an amended pleading within the time remaining for response to the original pleading or within 10 days after service of the amended pleading, whichever period may be longer, unless the Court otherwise orders.
(aa) Form of amendments. A party serving an amended pleading shall indicate plainly in the amended pleading in what respect the amendment differs from the pleading which it amends.
(b) Amendments to conform to the evidence. When issues not raised by the pleadings are tried by 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 so to amend does not affect 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 freely when the presentation of the merits of the action will be subserved thereby and the objecting party fails to satisfy the Court that the admission of such evidence would prejudice the party in maintaining the action or defense upon the merits. The Court may grant a continuance to enable the objecting party to meet such evidence.
(c) Relation back of amendments. An amendment of a pleading relates back to the date of the original pleading when
(1) relation back is permitted by the laws that provide the statute of limitations applicable to the action, or
(2) the claim or defense asserted in the amended pleading arose out of the conduct, transaction or occurrence set forth or attempted to be set forth in the original pleading, or
(3) the amendment changes the party or the naming of the party against whom a claim is asserted if the foregoing provisions of subdivision (2) of this paragraph are satisfied and, within the period provided by law for commencing the action against the party, the party to be brought in by amendment (A) has received such notice of the institution of the action that the party will not be prejudiced in maintaining a defense on the merits; and (B) knew or should have known that, but for a mistake concerning the identity of the proper party, the action would have been brought against the party.
(d) Supplemental pleadings. Upon motion of a party the Court may, upon reasonable notice and upon such terms as are just, permit the party to serve a supplemental pleading setting forth transactions or occurrences or events which have happened since the date of the pleading sought to be supplemented. If the Court deems it advisable that the adverse party plead thereto, it shall so order, specifying the time therefor.
Del. Fam. Ct. R. Civ. P. 15