How Does Option Vesting Work in a Prenup?

How a prenup handles option vesting, in short

A prenup lets a couple decide together how vested and unvested options and RSUs are classified if the marriage ends, overriding state default rules that would otherwise apply automatically. The agreement can specify whether each grant is separate property, shared property, or a mix, and it can include formulas for allocating straddle grants that were issued before the marriage but keep vesting after the wedding.

Grants that straddle the marriage line are the central complication. Without an explicit prenup clause, a court will apply its own time-based formula to decide what portion belongs to whom, and the outcome depends on your state. Each state's community property or equitable distribution defaults remain in effect unless your agreement specifically replaces them.

What stock options, RSUs, and vesting schedules mean for a prenup

Vesting timing, not just the grant date, determines what portion of equity is marital versus separate property. That distinction makes vesting schedules the single most important technical detail in an equity-heavy prenup.

Stock options give an employee the right to buy company shares at a fixed price (the "strike price") within a certain window. The financial value comes from the gap between the strike price and the market price at the time of exercise. If the market price never exceeds the strike price, the option can expire worthless. Options come in two tax flavors: Incentive Stock Options (ISOs) and Non-Qualified Stock Options (NSOs), each with different tax treatment at exercise.

Restricted Stock Units (RSUs) are a promise from an employer to deliver actual shares once certain conditions are met. Unlike options, you don't have to buy anything; the shares are simply granted to you when they vest.

Both types of equity follow vesting schedules that determine when you gain full ownership:

• Time-based cliff vesting: Nothing vests until you hit a milestone, often a one-year cliff. At that point, a chunk (commonly 25%) vests at once.
• Graded vesting: Equity vests in pieces over time, such as 25% per year over four years, or monthly after the initial cliff.
• Performance-based triggers: Vesting depends on hitting company or individual targets, a revenue goal, a funding round, or a liquidity event like an IPO.

Because vesting happens over time, a single grant can span your pre-marriage, marriage, and post-separation periods. That's why family courts focus on when equity vested, not just when it was granted.

How state law classifies equity earned during marriage

Your state's property system determines what happens to equity compensation by default, and a prenup is how you replace those defaults with rules you choose together.

Two systems govern marital property in the United States. Community property states generally treat property earned during the marriage as owned 50/50, regardless of whose name sits on the cap table. Equitable distribution states give courts broader discretion to divide marital property in a way deemed fair, which does not necessarily mean equally.

The nine community property states are Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, and Wisconsin. New York, Massachusetts, Florida, Illinois, and most other states (plus D.C.) use equitable distribution.

One important federal rule applies across all states: under 26 U.S.C. § 1041, spousal transfers of property incident to divorce are generally tax-free at the time of transfer. However, income tax still comes due when the recipient exercises options or sells shares. A prenup can address who bears the tax liability, but it cannot change the underlying tax law.

The straddle grant problem and time-based formulas

The hardest equity question in family law is the straddle grant: a stock option or RSU package granted before or during the marriage that vests after separation. Without a prenup, courts must decide what portion of an unvested grant is marital property and what portion is separate.

Most jurisdictions apply some version of a time-based fraction (sometimes called a "coverture fraction"). The numerator is the number of months of vesting that occurred during the marriage, and the denominator captures the total vesting period. The marital portion equals that fraction multiplied by the total shares that vested.

California has the most developed case law on straddle grants, with two well-known formulas:

• The Hug formula (Marriage of Hug, 1984) applies when options were granted primarily as an inducement to accept employment or as a reward for past service. The denominator runs from the date of grant to the date of vesting, because the grant itself is the relevant earning period.
• The Nelson formula (Marriage of Nelson, 1986) applies when grants are tied to future performance or continued service. The denominator runs from the start of employment to the date of vesting, capturing a longer earning period that includes pre-grant service.

Because the Nelson denominator is longer, it typically produces a smaller marital fraction for the same grant. Neither formula is mandatory. California courts retain broad discretion to adapt the approach to the facts of each case, and other states may apply their own variations or rely on general equitable principles.

A prenup can replace both formulas with a rule you and your partner agree on. You might choose the Hug approach, the Nelson approach, a flat percentage, or a different allocation entirely. The key is specificity: a generic clause saying "all stock options remain separate property" may not hold up if community efforts during the marriage contributed to vesting or growth.

How to address vesting in your prenup step by step

Following a structured process helps ensure your agreement is specific enough to be enforceable and fair enough that both partners feel good about it.

Step 1: Inventory every grant

List each stock option and RSU grant with its grant date, number of shares, strike price (for options), current vesting schedule, and vesting type (cliff, graded, or performance-based). Include grants that are already fully vested, partially vested, and entirely unvested. Incomplete disclosure of grants can void an equity clause, so thorough documentation matters.

Step 2: Choose a classification rule together

Decide how you want to treat each category:

• Pre-marital grants already vested: Typically classified as separate property, but state default rules may differ if gains accrued during the marriage.
• Pre-marital grants still vesting (straddle grants): Specify a formula for allocating the marital and separate portions. Reference a time-based fraction or agree on a fixed percentage.
• Grants issued during marriage: Decide whether these are shared, separate, or partially allocated. In community property states, they are shared by default unless your agreement says otherwise.
• Appreciation during the marriage: Address whether growth in value of separate-property equity remains separate or becomes shared.

Step 3: Build explicit formulas for straddle grants

Don't rely on a single sentence. Spell out the numerator (months of vesting during marriage) and denominator (total vesting period, from grant to vest or from employment start to vest), and define the relevant dates: marriage date, separation date, and vesting date. If you prefer a different method, describe it precisely.

Step 4: Plan for liquidity events and future grants

Equity compensation evolves. Your prenup should address:

• Acquisitions and mergers: What happens if accelerated vesting triggers during the marriage due to a buyout?
• IPOs: How is the value of previously illiquid equity treated once it becomes tradeable?
• Vesting after separation: Clarify which state's separation date applies and how post-separation vesting is allocated.
• Future grants: Consider a clause covering grants not yet issued, stating the classification rule that will apply.

Step 5: Ensure disclosure and independent counsel

Full financial disclosure is a prerequisite for enforceability. Attach a schedule listing every grant, and update it if new grants arrive between drafting and signing. Independent counsel for each partner is highly recommended for an enforceable prenup, and it is especially important when complex assets like equity compensation are involved.

Some states impose procedural requirements. California, for example, requires a minimum of seven calendar days between when a party receives the final agreement and when they sign it. Missing these requirements can make the entire agreement voidable.

A qualified attorney can help translate your intentions into enforceable language, and a financial advisor familiar with equity compensation can help value options, model tax scenarios, and clarify the practical implications of different formulas.

A checklist for equity-heavy prenups

Before you and your partner finalize your agreement, walk through this checklist together.

• [ ] Complete grant schedule attached: Every grant listed with date, share count, strike price, vesting type, and vesting timeline
• [ ] Classification rule defined: Separate, shared, or hybrid for pre-marital vested grants, straddle grants, marital grants, and future grants
• [ ] Straddle formula specified: Numerator, denominator, and relevant dates (marriage, separation, vesting) clearly described
• [ ] Appreciation treatment addressed: Whether growth on separate-property equity stays separate or becomes shared
• [ ] Liquidity events covered: Acquisition acceleration, IPO, and post-separation vesting scenarios included
• [ ] Tax allocation addressed: Who bears income tax on exercise or sale, consistent with 26 U.S.C. § 1041
• [ ] Disclosure attachments included: Current grant schedules, plan documents, and vesting confirmations
• [ ] Independent counsel confirmed: Each partner has their own attorney
• [ ] Waiting period met: Applicable state requirements (e.g., California's seven-day rule) satisfied
• [ ] Accounts maintained separately: Post-signing, keep separate-property equity in separate brokerage accounts to avoid co-mingling

As Michael C. Cotugno, Esq., Managing Partner of Neptune Legal, puts it: "The initial outreach for a premarital agreement is an invitation, not a demand." The goal is financial clarity for both partners, not a one-sided maneuver. Adhering to the agreement's terms throughout the marriage, particularly by keeping accounts consistent and avoiding co-mingling, is what keeps the agreement enforceable long after signing day.