Unless displaced by particular provisions of this Act, the principles of law and equity, including the law merchant, and the law relative to capacity to contract, principal and agent, estoppel, fraud, misrepresentation, duress, coercion, mistake, bankruptcy, or other validating or invalidating causes supplement its provisions.
12-643.Supplementary general principles of law.
Article XII. Judgments - Enforcement · Part 6. Foreign Judgments and Foreign-Money Claims · Not amended since adoption on record · Last verified July 20, 2026
In one sentenceConfirms that ordinary principles of contract and equity, capacity, agency, estoppel, fraud, duress, mistake, and bankruptcy, continue to fill gaps the Act itself doesn't address.
Full Text of 735 ILCS 5/12-643
Plain-English Summary
A uniform act can't anticipate every dispute, so this section confirms what fills the gaps: general principles of law and equity, including the law merchant and doctrines on capacity to contract, principal and agent, estoppel, fraud, misrepresentation, duress, coercion, mistake, and bankruptcy.
These principles apply unless a specific provision of the Act displaces them. The section doesn't create new claims or defenses; it preserves the background law a court would otherwise apply to a contract or claim dispute, layering the Act's currency-specific rules on top rather than replacing that body of law wholesale.
Frequently Asked Questions
Does the Act replace general contract and equity law?
No. This section confirms that ordinary contract and equitable principles keep applying, except where a specific Act provision displaces them.
What doctrines survive alongside the Act?
Capacity to contract, principal-and-agent law, estoppel, fraud, misrepresentation, duress, coercion, mistake, bankruptcy, and the law merchant, among other general principles.
Why include a supplementary-principles clause in a currency statute?
Because the Act addresses currency-specific questions only; without this section, it would be unclear whether ordinary contract and equity doctrines still apply to the underlying dispute.
Does this section create any new claim or defense?
No. It preserves existing law rather than adding to it.
How does a court decide whether the Act displaces a common-law principle?
Only where a specific provision of the Act conflicts directly with that principle; otherwise, the background doctrine keeps applying alongside the Act.
Amendment History
(Source: P.A. 86-1291.)
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: general contract law and the foreign money claims actcommon law principles supplementing a uniform actequity doctrines foreign money claim Illinoisfraud and duress defenses in a currency claim