You got married, and some time later something significant changed — you received a family inheritance, sold a business, came into a substantial gift, or simply realized the two of you had never addressed what would happen to the assets each of you brought into the marriage. A postnuptial agreement may be exactly the tool you need.
In Colorado, postnuptial agreements — called marital agreements under state law — are legally recognized and enforceable when properly drafted and executed. They can clarify asset ownership, protect inheritances, and prevent the kind of costly disputes that arise when separate and marital property become difficult to untangle. Here is what you need to know.
How Colorado Defines Separate vs. Marital Property
Colorado is an equitable distribution state. Under C.R.S. § 14-10-113(1), a court divides marital property in proportions it deems just after considering each spouse’s contributions, economic circumstances, the value of property set apart to each spouse, and changes in the value of separate property during the marriage. Equitable does not mean equal, but courts frequently arrive near an even split.
Under C.R.S. § 14-10-113(2), separate property includes assets owned before the marriage, property received by gift, bequest, devise, or descent, and property excluded by valid agreement of the parties. What many people do not expect is the appreciation rule: under C.R.S. § 14-10-113(4), any increase in the value of separate property during the marriage is treated as marital property subject to division. This means a premarital investment account worth $200,000 at marriage that grows to $350,000 by divorce has a $150,000 marital component — even if the account was never touched.
Income generated from separate property during the marriage is also marital property under Colorado law. Rental income from a separately-owned property, dividends from a premarital investment account, and royalties from assets you owned before the wedding are all potentially subject to division.
The Commingling Risk: How Separate Property Becomes Marital
One of the most common and costly mistakes people make is allowing separate property to become intertwined with marital assets — a process courts call commingling. Once that happens, what started as clearly separate property can become subject to equitable division, and the burden falls on the spouse claiming separate status to trace it back to its original source.
Commingling happens in predictable ways. Depositing an inherited sum into a joint checking account used for household expenses often converts those funds to marital property. Using an inheritance as a down payment on a home titled in both spouses’ names creates a presumption under Colorado law that a gift to the marital estate was intended. Paying recurring marital expenses — utilities, groceries, vacations — from an account funded by a gift or inheritance makes it nearly impossible to later argue the money remained separate.
Under C.R.S. § 14-10-113(3), all property acquired during the marriage is presumed to be marital property regardless of how title is held. The spouse seeking to establish separate status bears the burden of overcoming that presumption. Clear documentation — kept from the moment an asset is received — is essential. But documentation alone cannot undo commingling that has already occurred. That is where a postnuptial agreement becomes a far more reliable tool.
What a Postnuptial Agreement Can Do
A postnuptial agreement allows married spouses to contractually define which assets are separate property, how appreciation on those assets will be treated, and what happens to each spouse’s property in the event of divorce or death. Under C.R.S. § 14-2-302(2), a marital agreement is a written contract between spouses that affirms, modifies, or waives marital rights or obligations during the marriage or upon legal separation, divorce, or death.
For couples protecting separate property and inheritances, a postnuptial agreement can accomplish several things a carefully managed bank account cannot. It can designate a specific asset — real estate, a business interest, an investment portfolio, a family trust distribution — as separate property going forward. It can specify how appreciation on that asset will be treated, potentially keeping future growth in the separate property column rather than the marital one. And it can address what happens to income generated by separately-owned assets, which would otherwise be treated as marital property under default Colorado law.
Postnuptial agreements are increasingly used after a spouse receives a significant inheritance or family wealth transfer, after one spouse starts or acquires a business during the marriage, when a couple did not have a prenuptial agreement and wants to establish financial clarity, and when estate planning and family wealth protection goals are aligned.
Enforceability Requirements Under Colorado Law
Colorado adopted the Uniform Premarital and Marital Agreements Act (UPMAA) on July 1, 2014, codified at C.R.S. § 14-2-301 et seq. Both prenuptial and postnuptial agreements are governed by the same statutory framework. Under C.R.S. § 14-2-306, a marital agreement must be in writing and signed by both parties. No consideration is required — the agreement is enforceable as written without an exchange of value beyond the parties’ mutual consent.
Under C.R.S. § 14-2-307, a marital agreement is effective upon signing by both parties, unlike a prenuptial agreement which takes effect only upon marriage.
Under C.R.S. § 14-2-309, a postnuptial agreement is unenforceable if the party against whom enforcement is sought proves that consent was involuntary or the result of duress, that the party did not have access to independent legal representation, or that the agreement was unconscionable at the time of signing. Colorado courts apply heightened scrutiny to postnuptial agreements because they are signed within an ongoing confidential marital relationship, where the potential for one spouse to pressure the other is greater than in a premarital context. This makes full financial disclosure, adequate time to review, and independent counsel for each spouse especially important — not just best practices, but practical necessities for withstanding a future challenge.
Under C.R.S. § 14-2-310, certain provisions are unenforceable regardless of how the agreement is drafted. No postnuptial agreement can adversely affect a child’s right to support, waive custodial rights, penalize a spouse for filing for dissolution, or require either party to perform illegal acts.
Common Mistakes That Undermine Postnuptial Agreements
Even well-intentioned postnuptial agreements can fail at the moment they matter most — during a divorce proceeding. The following mistakes account for the majority of challenges and invalidations.
Using a generic template is one of the most common pitfalls. Fill-in-the-blank postnuptial agreement forms may not comply with Colorado’s UPMAA requirements and are rarely adequate for complex financial situations. An agreement that fails to specifically describe the assets it covers, or that uses ambiguous language about future appreciation, will not hold up to scrutiny.
Signing under pressure is another serious problem. An agreement presented during a marital crisis, alongside a threat of divorce, or without adequate time for review is vulnerable to a duress challenge under C.R.S. § 14-2-309. The timing and circumstances of signing matter as much as the document’s content.
Failing to make full financial disclosure undermines enforceability. Both spouses must have a fair and reasonable understanding of the other’s financial picture before signing. Courts have found that being “generally aware” of the other party’s circumstances can satisfy this standard, but significant gaps or deliberate omissions are grounds for invalidation.
Allowing only one attorney to draft the agreement without the other spouse having independent counsel creates real risk. While independent representation is not technically required by statute, the UPMAA requires that an unrepresented spouse sign a specific notice of waiver, and courts view one-sided drafting with skepticism.
Signing an agreement while actively planning to divorce is a critical error. Under C.R.S. § 14-2-303(3)(b), both parties must intend to remain married at the time of signing. An agreement entered into while dissolution is already being contemplated does not qualify as a marital agreement and will not be enforceable as one.
Why Postnuptial Agreements Are Increasingly Used After Significant Asset Events
Many couples do not think about a postnuptial agreement until something changes the financial landscape of the marriage. A parent passes away and leaves one spouse a substantial inheritance. A business built during the marriage reaches significant value. One spouse receives a large gift from family. The family farm is transferred to one spouse through an estate plan.
Each of these events creates a specific, identifiable asset with a defined value at a defined point in time. That clarity — right at the moment the asset is received — is exactly when a postnuptial agreement is most effective. Documenting the asset’s origin, its value, and the parties’ shared intent about its treatment in a properly executed agreement creates a record that is far stronger than documentation alone.
Waiting allows commingling to occur, appreciation to accumulate as a contested marital asset, and the original clarity of the moment to fade. The longer a couple waits after a significant asset event, the harder it becomes to establish clean separate property boundaries through a postnuptial agreement.
Talk to an Attorney Before Drafting
A postnuptial agreement is only as strong as its drafting and execution. Colorado’s UPMAA requirements are specific, courts scrutinize these agreements closely, and the consequences of an unenforceable agreement in a divorce can be severe — particularly when significant family wealth or a closely held business is involved.
At Tanis McGonegal Family Law, we help married couples think through their financial picture clearly and draft agreements that reflect their actual goals. Whether you have recently received an inheritance, want to protect a business interest, or simply want to establish financial clarity in your marriage, we are here to help you do it right.
Contact our office to schedule a consultation.
