In most states an inheritance is already your separate property — but that protection is fragile: one joint account, one mortgage payment, and commingling can make it divisible, with you bearing the burden of tracing every dollar. A prenup converts the default rule into a contract that survives commingling, covers income and appreciation, and can protect inheritances you haven't received yet.
The phone call comes the way it always does — a relative you loved, an account you never asked for, a number with more zeros than you expected.
You did nothing wrong. So you do the normal, well-meaning thing: the check goes into the joint checking account, because that’s where the mortgage gets paid. Two years later it funds the kitchen renovation. A few years after that, nobody — including you — can say with certainty which dollars of that account were ever yours alone.
That’s how a six-figure inheritance disappears one ordinary transaction at a time.
Here’s the good news: this is one of the most preventable financial problems engaged couples face. And a prenup can solve it — even for money you haven’t inherited yet.
The short answer
Yes — a prenup can protect your inheritance, and it can protect one you’ll receive someday. It can state that anything either of you inherits, before or during the marriage, stays the inheriting spouse’s separate property — along with the income and growth it produces — regardless of how it’s handled along the way.
The reason you need one isn’t that the law is against you. In most states, the law already starts on your side. The reason is that the law’s protection quietly erodes during ordinary married life, and the prenup is what stops the erosion.
The good news: inheritance is already separate property
In nearly every US state, property you receive by inheritance — from a will, a trust distribution, or the state’s succession rules — is the separate property of the spouse who received it, whether it arrives before the wedding or fifty years into the marriage. Unlike the paycheck you earn together, an inheritance addressed to one spouse generally isn’t divided in a divorce.
Many states put this in statute directly. So if the default rule already protects you, why is this article necessary?
Because the default rule protects the asset on paper — not what happens to it in your actual bank account.
The fragile part: how inheritances quietly become marital property
The legal word is commingling: mixing separate money with shared money until nobody can tell which is which. None of these require anyone to do anything wrong:
- Depositing the inheritance into the joint account used for household expenses
- Using inherited cash to pay down the mortgage on the jointly titled house
- Retitling inherited real estate into both spouses’ names
- Opening a joint brokerage account and moving inherited investments into it
- Paying years of family bills from the inheritance, without records
Once commingling happens, the burden shifts. Now you have to trace every dollar back to its separate source — bank statements going back a decade, the original will, tax returns, sometimes forensic accounting. Tracing is possible, but it’s slow, expensive, and dependent on records most people don’t keep. When the trail runs out, judges tend to treat the commingled balance as marital property and divide it.
There’s a second, subtler risk hiding here: growth. Even when the principal stays separate, the dividends, rent, and appreciation an inheritance produces during the marriage can be claimed as marital property in some states — especially if you actively managed the assets. The default rules answer this question differently depending on where you live.
What a prenup actually adds
A prenup doesn’t just repeat the law — it replaces the fragile parts of it with terms you two choose:
1. A classification that survives commingling. The agreement can say the inheritance remains separate property even if it passes through a joint account or is spent on the family home. Instead of tracing dollars years later, the written rule controls.
2. Income and appreciation, addressed explicitly. “The inheritance and anything it earns — dividends, rent, growth — stays mine.” One sentence closes a gap most couples never see coming.
3. A rule for inheritances that don’t exist yet. You don’t need to name a dollar amount that hasn’t happened. A category rule (“any inheritance either of us receives, from any source, at any time”) protects the future the same way the present is protected — and disclosing that you expect one (the source, a rough range) is exactly the kind of transparency courts like to see.
4. A decision about family-purpose use. Most people who inherit money eventually use some of it on the household — a down payment, a renovation. The prenup lets you choose what that means on purpose: reimbursed to you at divorce, or knowingly gifted to the marital estate. Both choices are legitimate. Choosing by accident is the problem.
5. Clean financial disclosure. Surprising your spouse with a family fortune — or hiding an expected one — is an omission that invites a challenge to the whole agreement. Full disclosure up front is protection for both of you.
The stronger pairing: trusts
If your side of the family has an estate plan, there’s a tool that works before the money ever reaches you: a trust. Assets held in a properly structured (often spendthrift) trust aren’t legally yours to commingle — there’s nothing to mix into the joint account because the control sits with the trustee.
The two tools cover different layers: the trust keeps inherited assets out of your personal ownership in the first place; the prenup covers whatever does reach your hands, plus the growth and income questions. One important limit: trust assets can still be reached by court order for support obligations — a trust protects against property division, not against child or spousal support orders.
And a related blind spot worth knowing: employer retirement plans (pensions, and some 401(k) arrangements) carry federal beneficiary rules that a prenup generally can’t override. When inheritances and retirement accounts overlap, that’s a conversation for your attorney.
If you’re already married
A postnuptial agreement does the same job after the wedding. The key window: while you and your spouse still agree on where the money came from. Once the marriage is in trouble, reestablishing separate character over commingled funds becomes a much harder — and more expensive — argument. If you’re married and expecting an inheritance, the time to paper it is now, not later.
Habits that strengthen the protection
A prenup is the strongest layer, but good habits reinforce it:
- Keep inherited funds in an account titled solely to you
- If you inherit property, keep the deed in your name and pay its expenses from that same separate account
- Never let inherited money flow through the household account “just for now”
- Keep the will, trust documents, and transfer records — forever
This is general information, not legal advice. Inheritance and property laws vary by state, and your family’s estate plan may add layers a prenup should be drafted to match.
Next: If you’re blending families, the estate side of this conversation is essential — Second Marriage? How to Protect Your Kids With a Prenup covers elective shares, beneficiary forms, and the talks that prevent fights. To see where inheritance sits in the bigger picture, start with what a prenup can and can’t cover, and if you’re weighing whether the document is worth it at all, is a prenup worth it?
