How to Prosecute a Colorado Postnuptial Agreement

By Matthew C. Clawson — Colorado Family Law Attorney

Postnuptial agreements, legally known as marital agreements, are common tools for financial planning in Colorado marriages. They determine how property will be classified, divided, or protected, and they may include spousal maintenance, debt allocation, and estate rights. If a postnuptial agreement is valid, Colorado courts must enforce it. However, to successfully prosecute (enforce) a postnup during divorce litigation, the proponent must understand the statutory framework governing these agreements and must present a clear, well-supported argument that the agreement meets the requirements of Colorado’s Uniform Premarital and Marital Agreements Act (“UPMAA”), C.R.S. §§ 14-2-301 to 14-2-310.

Colorado law begins with a powerful advantage for the party seeking to enforce the agreement. Under C.R.S. § 14-2-309(2), the spouse challenging the agreement bears the burden of proving unenforceability. This means the spouse prosecuting the agreement is not required to prove validity unless and until the opposing spouse establishes adequate grounds for invalidation. The presumption of enforceability is foundational and should be established early in the case.

Successfully prosecuting a postnuptial agreement begins by demonstrating that it complies with the four essential formation requirements set out in Colorado law. The agreement must be in writing and signed by both spouses under C.R.S. § 14-2-306. Evidence of proper signatures, notarization, and execution formalities should be introduced early and clearly. If the opposing spouse claims forgery, lack of signature, or lack of execution, offering the original signed document, testimony of witnesses, or notarial verification typically resolves this issue quickly.

The next step in prosecution involves establishing voluntariness. Under C.R.S. § 14-2-309(1)(a), an agreement is unenforceable only if the spouse proves they did not sign voluntarily. The proponent should provide evidence showing that the signing spouse had time to review the agreement, was not pressured or threatened, and was fully aware of what they were signing. Emails, text messages, and drafts exchanged between the parties or counsel are especially persuasive in showing that negotiation occurred without coercion. The more transparent and collaborative the negotiation process appears, the more difficult it is for the challenging spouse to meet the burden of proving duress.

Prosecution also requires demonstrating that the challenging spouse either had independent counsel or knowingly waived the right to independent counsel. C.R.S. § 14-2-309(1)(b)–(c) outlines these requirements. If a spouse had counsel, the representation letter, engagement agreement, or communications with counsel may be used to demonstrate adequate representation. If the spouse waived counsel, the written waiver and statutory notice of rights must be introduced. The proponent should highlight any evidence that the spouse was encouraged to seek counsel, had time to do so, understood the waiver, and declined counsel voluntarily.

Another key component in prosecuting a postnuptial agreement is demonstrating that adequate financial disclosure occurred. Under C.R.S. § 14-2-309(1)(d), the opposing spouse must prove they did not receive reasonably accurate information about the other spouse’s income, property, and financial obligations. To prosecute effectively, the supporting spouse should produce the financial disclosure materials exchanged during negotiation, including tax returns, bank records, business documents, retirement statements, debt summaries, and financial declarations. Testimony may also be used to establish that the challenging spouse was familiar with the parties’ finances, had access to records, or participated in financial management during the marriage.

If the challenge involves spousal maintenance or attorney fee provisions, the proponent must reinforce the statute’s distinction between general enforceability and unconscionability at the time of enforcement. Under C.R.S. § 14-2-309(5), maintenance provisions may be invalidated only if they are unconscionable at the time they are enforced. To prosecute the agreement, the supporting spouse should present evidence showing that the opposing party will not be left impoverished or unable to meet reasonable needs. Demonstrating that the spouse receives substantial property, sufficient income, retirement assets, or the ability to earn an income often defeats unconscionability claims. Courts do not invalidate maintenance waivers merely because they are strict or one-sided; the waiver must be fundamentally unfair under current circumstances.

Intent to remain married at the time of signing is another statutory requirement central to every prosecution. C.R.S. § 14-2-302(2) requires that the agreement be signed by spouses intending to continue their marriage. The proponent should present communications or testimony reflecting the marital context of the agreement—such as reconciliation efforts, financial planning discussions, or estate planning objectives. This counters any argument that the agreement was a disguised separation agreement, which would violate C.R.S. § 14-2-303(3)(b). Persuasive authority, such as the Colorado Court of Appeals’ interpretation in In re Marriage of Kinning supports the principle that thinking about divorce does not invalidate a postnup so long as the parties intended to remain married when they signed it.

To prosecute a postnup effectively, the proponent should rely not only on statutory compliance but also on evidence of fairness in process. Courts examine the negotiation process, the clarity of the terms, and the presence of mutual understanding. Well-drafted agreements that clearly define property rights, list assets, and include exhibits or schedules are far more likely to be enforced. Testimony demonstrating that both spouses understood the agreement, asked questions, and reviewed drafts helps establish that the agreement was entered into knowingly and voluntarily.

If the opposing spouse attempts to invalidate the entire agreement by attacking a single clause—such as a child-related provision or a punitive clause—the proponent should rely on Colorado’s rule of partial enforceability. Under C.R.S. § 14-2-310, only the terms that are prohibited or contrary to public policy are unenforceable; the remainder of the agreement is preserved. This means that even if a single clause is invalidated, the financial portion of the postnup almost always survives.

The most persuasive evidence in prosecuting a Colorado postnuptial agreement includes the original signed and notarized agreement, financial disclosures exchanged at signing, previous drafts, written communications between spouses or attorneys, witness testimony confirming knowledge and voluntariness, and evidence of reasonable financial conditions at the time enforcement is sought. Together, these elements typically satisfy the UPMAA’s requirements and make the agreement highly likely to be enforced.

Colorado courts consistently uphold postnuptial agreements when the statutory requirements have been met. Clear evidence of voluntary execution, adequate disclosure, compliance with the statutory notice requirements for unrepresented spouses, and a straightforward negotiation process usually results in enforcement. High-asset divorces, business owner divorces, and complex marital estates depend heavily on these agreements, making prosecution strategy a critical skill for family law litigators.

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Matthew C. Clawson, Colorado Family Law Attorney
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Legal Disclaimer- This article is for informational purposes only and does not constitute legal advice. Reading this content or contacting the attorney does not create an attorney-client relationship. Legal decisions and outcomes depend on the specific facts of each case. Colorado laws may change, and you should consult a licensed attorney for advice tailored to your circumstances. No guarantee is made regarding the accuracy or completeness of the information provided.