Prenup vs. Postnup: What's the Difference?

Family lawyers all agree on one point: Couples that have honest and open communications about money and shared financial goals are able to build better and healthier long-term partnerships. That’s why it’s crucial for you and your partner to proactively have conversations about these money and shared financial goals, even if it may be uncomfortable or unromantic at first. 

A prenup or postnup can act as an effective driver for both partners to discuss shared financial goals and what matters when building an effective partnership down the road. Either could be a good idea for your relationship depending on what your circumstances are. 

Let’s first clear up a common misconception. Prenuptial and postnuptial agreements aren't about anticipating the worst. In fact, we would argue they are the complete opposite. It may be counterintuitive, but the nature of these agreements allow couples to sit down and talk about both sides of the equation: what happens when you both stay together and what happens when you both separate. The discussions of best case and worst case scenarios actually end up helping you and your partner build  a shared roadmap to understand where you're headed and how you’ll get there together.

So, how do they differ? And how do you know which one fits your situation?

We’ll break down how prenuptial and postnuptial agreements work, when they’re used, and why couples are increasingly using them as part of their financial planning.

What is a Prenup? 

A prenuptial agreement is a personalized financial plan you and your partner create before tying the knot. It’s a way to openly discuss financial goals, expectations, and how you want to handle money-related matters together, now and in the future.

At Neptune, we think of it as an advanced form of financial transparency. You’re essentially saying: “Let’s get on the same page from the start.”

Where prenups can be especially helpful is with the following: 

• One or both partners have pre-existing financial assets
• You want clarity around future financial decisions like purchasing your first marital home together
• You're blending different financial habits or have a disparity in incomes
• You're building a modern partnership together and want to lead with intention

What Is a Postnup?

A postnuptial agreement, or postnup, serves a similar purpose, but it is created when you’re already married. Fun fact, oftentimes, couples who go through estate planning may have postnups as a part of their legal documents.   

Timing often necessitates a postnup over a prenup. For instance, a couple may have intended to sign a prenup but ran out of time before the wedding. Certain states require prenups to be signed well in advance of the wedding. For example, California requires a 7 day waiting period between finalizing the prenup and signing the agreement. In general, if the timeline of the prenup was rushed, the agreement may not hold up in court. One partner might be able to argue that they signed under pressure or duress.

In other cases, life has simply changed after marriage. A career move, a new business venture, or an inheritance may lead you to revisit how you manage finances together. Or perhaps, you’ve noticed your roles and expectations evolving - like someone taking a step back from their career to raise children - and want to reflect that in a formal agreement.

A postnup offers you both a chance to pause and recalibrate:

• Have our financial habits changed?
• Are we aligned on how we manage personal and shared resources?
• Do we want to update how financial decisions are made moving forward?

Like a prenup, a postnup invites open dialogue about values, commitments, and long-term planning—just at a different point in your relationship.

What Can Be Included in a Prenup or Postnup?

Whether it’s a prenup or a postnup, the focus is on how you will handle financial matters both now and in the future.

These agreements can cover:

• Income, investments, and savings
• Existing or shared debts
• Ownership of assets, including but not limited to property, equity, and other investments
• Guidelines for long-term financial decisions
• Plans for supporting each other through education, career transitions, or caregiving

The specifics may vary, but both types of agreements are meant to reduce uncertainty, foster open conversations, and help create shared expectations. The main difference in the prenup vs postnup discussion comes down to timing, i.e., before or after the wedding, and not the intent.

Are Prenups and Postnups Legally Binding?

Yes, both prenups and postnups can carry legal weight if certain conditions are met. To create a sound prenup or postnup, it also is important that you and your partner have your own legal representation. Each state has its own laws, but in general, for an agreement to hold up in court, it should be:

• Voluntary: Both partners should have entered into it freely, without pressure
• Transparent: There must be full financial disclosure from both sides
• Fair: The terms should be reasonable and not heavily one-sided
• Properly executed: It must be a written and signed document, executed with enough time for review and legal counsel

Prenup or Postnup: It’s Really About Partnership

Talking about money isn’t always easy, but it’s essential. Choosing between a prenup and postnup isn’t about which document is “better,” but which supports your timing, goals, and shared vision. 

This is where Neptune comes in.

We’re not just here to check a box or draft paperwork. We help couples have the right conversations, at the right time, with guidance that’s thoughtful, human, and tailored to your life together.

Whether you’re planning ahead or reassessing your financial picture after marriage, Neptune offers support that goes beyond the legal. We ensure you both feel informed, confident, and aligned on what comes next. Start the conversation with Neptune today.