Supplemental pleadings, setting up matters which arise after the original pleadings are filed, may be filed within a reasonable time by either party by leave of court and upon terms.
2-609.Supplemental pleadings.
Article II. Civil Practice · Part 6. Pleading · Not amended since adoption on record · Last verified July 20, 2026
In one sentenceA party may file a supplemental pleading to raise matters that arose after the original pleading, but only with the court's leave, within a reasonable time, and on whatever terms the court sets.
Full Text of 735 ILCS 5/2-609
Plain-English Summary
Section 2-609 is short but fills a real gap: it lets a party bring new, later-arising facts into a pending case without starting over. A supplemental pleading covers matters that arise after the original pleading was filed -- something an amendment, which reaches back to facts existing at the time of filing, cannot properly do.
Access to that tool isn't automatic. A party needs leave of court, must act within a reasonable time after the new matter arises, and takes the supplemental pleading subject to whatever terms the court imposes, which might include a deadline for the opposing side to respond or conditions tied to any delay.
This section complements 2-616, which governs amendments to pleadings covering facts that already existed when the original pleading was filed. Together they cover both directions a pleading might need to grow: backward-looking correction through amendment, and forward-looking supplementation for new developments.
Frequently Asked Questions
What is a supplemental pleading for?
It lets a party set up matters that arose after the original pleading was filed -- new facts or events the original pleading couldn't have addressed.
Can a party file a supplemental pleading without asking the court first?
No. Section 2-609 requires leave of court before a supplemental pleading may be filed.
Is there a deadline for filing a supplemental pleading?
The section requires it be filed within a reasonable time after the new matter arises, rather than setting a fixed number of days.
How is a supplemental pleading different from an amendment under 2-616?
An amendment addresses facts and claims tied to the original filing date; a supplemental pleading addresses matters that arose only after the original pleading was already on file.
Can the court attach conditions to allowing a supplemental pleading?
Yes. The section allows the court to grant leave upon terms, giving it room to set conditions appropriate to the case.
Amendment History
(Source: P.A. 82-280.)
Source & verification. Section text and amendment history are
reproduced verbatim from the Illinois Compiled Statutes, published by the
Illinois Compiled Statutes, Illinois General Assembly / Legislative Reference Bureau. Last verified July 20, 2026.
· Official source
Also known as: supplemental pleading illinoisnew facts after complaint filed illinoissupplement a pleading illinois civil case