A "sunset clause" is one of the more talked-about prenup terms, and the idea behind it is simple: the agreement, or part of it, comes to an end — or changes — after a set period of time or a particular life event. If you have heard that a prenup can "expire" after so many years, a sunset clause is what makes that happen. This guide explains how sunset clauses work, when they make sense, when they do not, and the alternative most couples end up preferring.
How a sunset clause works
A sunset clause sets a trigger, after which the prenup expires or its terms soften. The trigger can be a number of years of marriage (say, the agreement falls away after 15 years), or a life event such as the birth of a child or a significant wedding anniversary. Some clauses switch the agreement off entirely; others taper it, so protection reduces gradually rather than vanishing overnight. The clause sits alongside the other terms covered in prenup clauses explained.
Common sunset triggers
- A fixed number of years — for example, the agreement lapses after 10, 15 or 20 years of marriage.
- The birth of a child — the couple agree to revisit everything once children arrive and needs change.
- A milestone anniversary — a symbolic point at which a long, settled marriage is no longer governed by an early agreement.
- A tapering formula — protection reduces in stages the longer the marriage lasts.
The case for a sunset clause
Sunset clauses can make a prenup feel fairer and easier to agree to, because neither partner is bound forever regardless of how life turns out. The logic is intuitive: a long, settled marriage arguably should not be governed by an agreement signed decades earlier, when the couple were different people in a different financial position. That perceived fairness can actually help the agreement, since fairness is central to whether a court will give it weight. For couples who feel uneasy about the idea of a permanent contract, a sunset clause can be what makes a prenup acceptable at all.
The case against
The flip side is uncertainty: the protection you wanted simply disappears at the trigger point — which may be exactly when there is most to protect. If your goal is to safeguard a business, an inheritance or a pension for the long term, a hard expiry can defeat the whole purpose. A business is often far more valuable after 15 years than on the wedding day, so a sunset clause that lapses at year 15 removes the protection at the worst possible moment.
The alternative: review, don’t expire
Many couples prefer a review clause — a commitment to revisit and, if needed, update the agreement as life changes — over an automatic sunset. It keeps the protection in place while still keeping things fair, because you can adjust the terms deliberately rather than letting them vanish on a fixed date. In practice, review gives you the flexibility people want from a sunset clause without the loss of protection. Our pillar guide to what to include covers both.
Sunset clause vs review clause: which to choose
| Feature | Sunset clause | Review clause |
|---|---|---|
| What happens over time | Agreement expires or softens automatically | Agreement is revisited and updated by agreement |
| Long-term protection | Ends at the trigger | Continues, adjusted as needed |
| Best for | Couples wanting a time-limited deal | Protecting a business, inheritance or pension long term |
| Risk | Protection gone when most needed | Requires you both to actually do the review |
Should your prenup have a sunset clause?
Whether to include a prenup sunset clause comes down to what you are protecting. If the aim is simply to keep things fair over a long marriage, a sunset clause — letting the agreement lapse after, say, 15 years or the birth of a child — can feel reasonable and even help it hold up. But if you are protecting a business or inheritance for the long term, a sunset clause removes the protection at the very point you may need it; a review clause is usually the better tool.
A worked example: when a sunset clause backfires
Imagine Sam starts a small business worth £50,000 when he marries, and the couple agree a sunset clause that lets the prenup lapse after 15 years, reasoning that a long marriage should not be governed by an early deal. Over those 15 years the business grows into a company worth £2 million — built partly on Sam’s pre-marital effort and partly on the years the couple invested together. On the day the clause expires, all of that protection falls away at once. Had they used a review clause instead, they could have sat down at year five and year ten, acknowledged the shared contribution, and agreed a fair split of the growth while still ring-fencing the original stake. The lesson is not that sunset clauses are always wrong — it is that a hard expiry is a blunt instrument for an asset that changes value over time.
Tapering: a middle path
Not every sunset clause switches the agreement off overnight. A tapering clause reduces protection in stages — for example, ring-fencing 100% of a pre-marital asset for the first five years, 75% for the next five, and so on. This can feel fairer than a cliff edge, because it reflects the intuition that the longer a couple share their lives, the more of what each brought in becomes genuinely joint. It maps loosely onto how a court already treats non-matrimonial property, which tends to be drawn into the shared pot the longer a marriage lasts. If you like the idea of a sunset clause but worry about the cliff edge, a taper is worth discussing when you take advice.
Does a sunset clause affect enforceability?
A prenup is not automatically binding in England & Wales. Since Radmacher v Granatino (2010) a court gives a properly made agreement significant weight, but it keeps a discretion under the Matrimonial Causes Act 1973 and will not enforce terms that leave a partner in real need. A sunset clause does not change that framework; it simply sets when the terms stop applying. It can make an agreement look fairer at the outset, which helps, but it is the whole package — disclosure, independent advice, good timing and fair terms — that decides how much weight the agreement carries.
Drafting a sunset clause well
If you do include one, be precise. Spell out exactly what triggers it (a date, an anniversary, the birth of a child), exactly what happens when it triggers (does the whole agreement fall away, or only part?), and what governs the position afterwards. Ambiguity here is dangerous: a vaguely worded sunset clause can leave both partners arguing about whether the prenup still applies at all. It is also worth pairing any sunset clause with a review clause, so that as the trigger date approaches you deliberately revisit the position rather than letting protection vanish by default. See what to include in a prenup for how these terms sit alongside the rest of the agreement, and does a prenup expire? for the default position when there is no sunset clause at all.
What the law already does to an old prenup, and why that shapes the choice
A sunset clause is a private answer to a question the law asks anyway. Under the test in Radmacher v Granatino an agreement is given effect unless, in the circumstances prevailing at the divorce, it would not be fair to hold the parties to it. Those words mean the court already looks at how life has changed since signing. An agreement that made no provision for children born later, or for a partner who gave up a career, is the classic example of one that has become unfair with time, and the court will depart from it whether or not it contains an expiry date.
That is the strongest argument against a hard sunset. If the agreement will in any case be judged against the circumstances at the divorce, an automatic expiry after fifteen years removes protection for pre-marital assets and inheritances at exactly the point when a long marriage makes them most likely to be treated as shared. The Supreme Court's 2025 decision in Standish v Standish confirmed that non-matrimonial property stays outside the sharing principle unless the couple have over time been treating it as shared; a prenup that says it is to stay separate is the best evidence that they have not, and a sunset clause deletes that evidence on a date chosen in advance.
The needs safeguard is the other reason a sunset is rarely necessary. Section 25 of the Matrimonial Causes Act 1973 requires the court to meet each partner's reasonable needs, and section 34 makes void any term that tries to stop either of them applying, so a partner who would be left short after a long marriage is protected without the agreement having to lapse. A review clause achieves what a sunset clause is usually for, keeping the agreement fair as circumstances change, without giving up the protection, and it also gives you the moment to make the fresh financial disclosure and take the independent legal advice that keep the agreement credible.
Prenup sunset clause: FAQs
What is a sunset clause in a prenup?
A term that makes the agreement expire or soften after a set time or event, such as a number of years of marriage or the birth of a child.
Is a sunset clause a good idea?
It depends what you are protecting — for long-term assets a review clause is often better.
Does a prenup expire without a sunset clause?
No — without one, a prenup stays in place until you change it (see does a prenup expire?).
Can you remove a sunset clause later?
Yes — you can update the agreement by a postnup, following the same good practice of disclosure, advice and fair terms.
Does a sunset clause make a prenup more likely to hold up?
It can, by making the agreement look fair, but it is the overall fairness and proper making of the agreement that matter most (see how to make a prenup fair).
What is a tapering sunset clause?
One where protection reduces in stages rather than ending all at once — for example ring-fencing less of a pre-marital asset the longer the marriage lasts.
Should a sunset clause be triggered by having children?
Some couples choose this, because children reshape both partners’ needs; others prefer a review clause so the agreement is updated rather than scrapped.
Is a sunset clause common in UK prenups?
They appear, but review clauses are more common here, because most couples want to keep protection in place while still adapting to change.
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UK Prenup is not a law firm and does not provide legal advice. A prenuptial agreement in England & Wales is not automatically binding, and both partners should take independent legal advice before signing.