If you don’t sign a prenup, your state’s default divorce and inheritance rules decide what happens to your property, your debts, your retirement accounts, and your spouse’s claim on your estate. Those defaults were written for the average couple, and they apply the same way to a two-year marriage and a thirty-year one, to a dentist married to a teacher and to two software engineers with identical paychecks. They are not necessarily unfair, but they are rigid, and they often produce results neither spouse would have agreed to in advance.
Here is what the defaults actually do.
Your Property Gets Sorted Into Two Buckets
Before anything can be divided, every asset and debt has to be classified as either separate property or marital property. Separate property is what you owned before the wedding, plus anything you inherited or received as a personal gift during the marriage, as long as you kept it apart from joint finances. Marital property covers almost everything acquired during the marriage, no matter whose name is on the title or account. Your paycheck, the house you bought after the wedding, the money you contributed to a 401(k) during the marriage — all marital.
The line is less clean than it sounds. Commingling can quietly convert separate property into marital property. Deposit an inheritance into the joint checking account you use for household bills, and it starts to lose its separate character. Use money you had before the wedding to renovate a jointly owned home, and the same thing happens. Once the money mixes, the spouse who wants to keep it separate has to trace the funds back to their original source. Without clean documentation, courts generally treat the whole commingled asset as marital.
A prenup lets couples draw their own lines. Without one, the state draws the lines, and courts apply them strictly.
How Assets and Debts Get Divided
Once property is sorted, one of two systems governs the split.
Community Property States
Nine states follow community property principles: Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, and Wisconsin. The common assumption is that this means an automatic 50/50 split, which isn’t entirely accurate. Some of these states start with an equal-division presumption; others, like Texas, require only a “just and right” division, which can come out uneven.1Justia. Community Property vs. Equitable Distribution in Property Division Law The label tells you how assets are classified, not that the split will always be even.
Equitable Distribution States
The other 41 states use equitable distribution, which divides marital property in a way the court considers fair rather than equal. Judges weigh the length of the marriage, each spouse’s income and earning capacity, age and health, and non-financial contributions like raising children or managing the household.1Justia. Community Property vs. Equitable Distribution in Property Division Law A spouse who left the workforce for a decade to raise children might come out with more than half, or less, depending on the full picture.
Debts follow the same framework. Credit cards, car loans, and mortgages taken on during the marriage are generally marital debt, even when only one name is on the account. Student loans incurred during the marriage often fall into the marital category too, especially when the education boosted household income. Courts look at timing, who benefited, and who signed.
The Assets That Cause the Biggest Fights
The defaults handle salaries and bank accounts cleanly enough. They handle complicated assets poorly, which is where divorces without prenups tend to get expensive.
A Business One Spouse Owned Before the Marriage
A business owned before the wedding may stay separate property. Its increase in value during the marriage often doesn’t. Most states distinguish between active appreciation, meaning growth driven by a spouse’s labor or the investment of marital funds, and passive appreciation, meaning growth from market or industry forces. Active appreciation is generally treated as marital and divided. Passive appreciation generally stays separate.
The stakes are significant. A business worth $200,000 at the wedding and $1.2 million at divorce has $1 million in appreciation to classify. If the owning spouse ran the company day-to-day, and especially if marital savings were reinvested, courts will likely treat much of that growth as marital property. The non-owner spouse ends up with a credible claim on a share.
Retirement Accounts
Employer-sponsored retirement plans like 401(k)s and pensions are governed by the federal Employee Retirement Income Security Act, which generally bars assigning plan benefits to anyone other than the participant.2Office of the Law Revision Counsel. 29 U.S. Code 1056 – Form and Payment of Benefits The exception is a Qualified Domestic Relations Order, a court order instructing the plan to pay a portion of benefits to a former spouse. Without one, the plan administrator cannot legally release anything to the non-participant spouse. The QDRO has to name both parties, identify the plan, and state the exact amount or percentage, and it cannot award benefits the plan doesn’t offer.3IRS. Retirement Topics – QDRO: Qualified Domestic Relations Order Drafting errors cause rejections that delay distribution for months.
Professional Degrees
Most states do not treat a professional degree or license earned during the marriage as marital property. You cannot hand over half a medical license. But courts routinely factor the degree into other parts of the divorce. If one spouse worked to put the other through medical school, that sacrifice will likely influence both spousal support and the overall property split. The degree stays with the person who earned it; its effect on earning capacity shapes everything else.
Whether You’ll Pay or Receive Spousal Support
Without a prenup setting support terms, a judge has broad discretion to order one spouse to pay the other after divorce. Alimony is meant to help the lower-earning spouse keep a reasonable standard of living or transition to independence.
It isn’t automatic. Courts look at several factors before ordering it:
- Whether the requesting spouse has genuine financial need and whether the other has the ability to pay.
- The length of the marriage. Longer marriages produce longer and larger support obligations; short marriages rarely result in extended alimony.
- Age and health, particularly health limitations that affect employability.
- Non-financial contributions like homemaking and childcare.
- The standard of living the couple maintained during the marriage, used as a benchmark.
Duration varies widely. Shorter marriages often produce rehabilitative support lasting a few years, enough time for the lower-earning spouse to build skills or re-enter the workforce. Marriages lasting 15 to 20 years or more can produce support obligations extending much longer, sometimes indefinitely. Formulas and caps differ sharply from state to state, which makes going without a prenup especially unpredictable for high earners.
The Tax Rules You Inherit by Default
Alimony Is No Longer Deductible
For any divorce or separation agreement executed after 2018, the paying spouse cannot deduct alimony, and the receiving spouse does not include it in taxable income.4IRS. Topic No. 452, Alimony and Separate Maintenance The Tax Cuts and Jobs Act shifted the full tax burden onto the payer. Before 2019, payers could deduct alimony, which effectively split the tax cost between both parties. Now the payer sends after-tax dollars, which makes support obligations more expensive in real terms than most people expect.
Property Transfers Carry Hidden Tax Basis
Under federal law, transferring property between spouses or former spouses as part of a divorce triggers no taxable gain or loss. The receiving spouse takes over the transferring spouse’s original tax basis.5Office of the Law Revision Counsel. 26 U.S. Code 1041 – Transfers of Property Between Spouses or Incident to Divorce The transfer itself is tax-free, but the built-in gain travels with the asset. Receive a stock portfolio with a $50,000 cost basis and a $300,000 current value, and you owe nothing at transfer. Sell it, and you face tax on $250,000 in gains. A 50/50 split on paper can produce very unequal results after taxes.
To get this treatment, the transfer has to happen within one year after the marriage ends or otherwise be related to the divorce.5Office of the Law Revision Counsel. 26 U.S. Code 1041 – Transfers of Property Between Spouses or Incident to Divorce Transfers years later without a clear connection to the divorce may not qualify, and the tax bill can come as a surprise.
What Happens If Your Spouse Dies
The absence of a prenup matters just as much when a marriage ends by death. State laws protect surviving spouses from disinheritance, even when a will says otherwise.
The Elective Share
Nearly every state gives a surviving spouse the right to claim a minimum portion of the deceased spouse’s estate regardless of what the will says. The surviving spouse can accept what the will provides or override it and claim the statutory share instead.6Legal Information Institute. Elective Share
The size depends on the state. Traditional-approach states use a flat fraction, typically one-third of the estate.6Legal Information Institute. Elective Share States following the Uniform Probate Code use a sliding scale tied to the length of the marriage, starting at 1.5% of the augmented estate for marriages under a year and climbing to a maximum of 50% at 15 years or more. The theory is that marriage is an economic partnership that deepens over time.
Many states calculate the elective share against the “augmented estate,” which is broader than the probate estate alone. The augmented estate includes nonprobate transfers like jointly held property, life insurance proceeds, and assets in revocable trusts. This prevents a spouse from quietly disinheriting the survivor by shifting assets outside the will, and it also limits the share when the surviving spouse has already received substantial assets outside probate.7Legal Information Institute. Augmented Estate
The elective share has to be claimed within a deadline set by state law. Miss the window and the right is gone. A common framework requires filing within nine months of death or six months after the will is admitted to probate, whichever comes later. A prenup can waive or modify the elective share, which is one reason estate planners push for them in second marriages where each spouse wants to protect assets for children from a prior relationship.
If There Is No Will at All
Without a will, state intestacy laws control. The surviving spouse’s share depends on whether the couple had children and whether either spouse had children from a previous relationship. When all children belong to both spouses, or when there are no children, the surviving spouse typically inherits the entire estate. When either spouse has children from a prior relationship, the surviving spouse generally receives a fixed dollar amount plus a percentage of the remainder. Formulas vary by state, but the pattern holds: the surviving spouse’s share shrinks when stepchildren are in the picture.
What No Prenup Would Have Changed Anyway
A few outcomes are the same whether you signed a prenup or not. Child custody and child support cannot be predetermined by any agreement between spouses. Courts decide those based on the child’s best interests at the time of divorce, and the Uniform Premarital and Marital Agreements Act, adopted in a growing number of states, explicitly makes agreement terms that adversely affect a child’s right to support unenforceable.8Uniform Law Commission. Uniform Premarital and Marital Agreements Act
Social Security rules are also outside a prenup’s reach. A divorced spouse can claim benefits on an ex-spouse’s earnings record only if the marriage lasted at least 10 years, and a surviving spouse generally must have been married for at least nine months before the spouse’s death to qualify for survivor benefits.9Social Security Administration. Who Can Get Survivor Benefits Nothing you could have signed changes that. But the 10-year mark is worth knowing if divorce is on the horizon and you’re close to it.
Already Married? A Postnup Is Still an Option
Couples who are already married and wish they’d signed something aren’t stuck with the defaults forever. A postnuptial agreement works much like a prenup but is signed after the wedding. It can address property division, spousal support, and debt allocation, giving a married couple a way to opt out of state defaults even years in.
Postnups face tougher scrutiny than prenups because spouses already owe each other fiduciary duties. Under the Uniform Premarital and Marital Agreements Act, a marital agreement has to be in writing, signed by both parties, and entered into voluntarily. A court will throw it out if the challenging spouse can show the agreement was signed under duress, that they lacked access to independent legal representation, or that the other spouse failed to provide a reasonably accurate picture of their finances before signing.8Uniform Law Commission. Uniform Premarital and Marital Agreements Act Full financial disclosure and separate lawyers for each spouse are the two requirements that matter most in practice. A postnup drafted at the kitchen table without counsel is an invitation to have it invalidated later.