(1) Where after the institution of a suit, a new plaintiff or defendant is substituted or added, the suit shall, as regards him, be deemed to have been instituted when he was so made a party:
Provided that where the court is satisfied that the omission to include a new plaintiff or defendant was due to a mistake made in good faith it may direct that the suit as regards such plaintiff or defendant shall be deemed to have been instituted on any earlier date.
(2) Nothing in sub-section (1) shall apply to a case where a party is added or substituted owing to assignment or devolution of any interest during the pendency of a suit or where a plaintiff is made a defendant or a defendant is made a plaintiff.
Legal Commentary & Landmark Judgments: Section 21
Section 21 of the Limitation Act, 1963 regulates the limitation consequences of substituting or adding a new plaintiff or defendant to an existing civil suit.
However, the proviso creates a vital equitable exception: if the court is satisfied that the omission to include the new plaintiff or defendant was due to a mistake made in good faith, it may direct that the suit shall be deemed to have been instituted on any earlier date—including the original date of institution of the suit. Sub-section (2) clarifies that Section 21 does not apply to the addition of legal representatives upon death or assignment of interest under Order XXII CPC.
When moving an application to implead a party under Order I Rule 10 CPC after limitation has expired, counsel must explicitly pray for the benefit of the proviso to Section 21(1), establishing that the omission arose from a bona fide mistake of fact or law, and not deliberate tactical omission.