“We were basically married already.” It’s something family lawyers hear a lot when a client describes their long-term relationship — only some years later comes the wedding, often followed (sadly) by separation. But legally, does that pre-marital cohabitation count for anything?

The Legal Question: When Does a Marriage Really Begin?

When the court is deciding how to divide assets after a divorce, one of the key factors is the duration of the marriage (under section 25(2)(d) of the Matrimonial Causes Act 1973). A longer marriage may lead to a more equal division — especially in a ‘sharing’ case — whereas a shorter one might justify ringfencing pre-acquired wealth.

So, here’s the rub: what if you lived together for years before tying the knot? Is that history wiped clean the day you say, "I do"?

The Seamless Transition Principle

Not necessarily. In a line of cases starting with GW v RW [2003], the courts have recognised that where a couple moves seamlessly from cohabitation into marriage without any major change in the way they live, it can be artificial to separate those periods.

As Mostyn J put it:

“Where a relationship moves seamlessly from cohabitation to marriage without any major alteration in the way the couple live, it is unreal and artificial to treat the periods differently.”

This approach allows the court to view the relationship as a continuous whole — particularly relevant when assessing contributions and needs.

So What Counts as Cohabitation?

It’s more than just sharing a postcode or spending a lot of time together. Later cases (like McCartney v Mills McCartney [2008] EWHC 401 (Fam), IX v IY [2018] EWHC 3053 (Fam), and VV v VV [2022] EWFC 41) have outlined what the court will look for:

• A mutual commitment — emotionally and practically
• Some level of financial interdependence
• Shared lives, even if not in a traditional domestic setup
• The parties’ intentions — did they see themselves as life partners before marriage?

Notably, simply being engaged, going on holidays, or even staying over regularly isn't enough. But if the couple were functioning as a unit — running a household, sharing finances, making life plans — that period might be considered when determining the length of the marriage.

Why It Matters

If you're divorcing after (say) two years of marriage but spent five years cohabiting beforehand, the court may take those earlier years into account — potentially shifting the outcome when it comes to dividing property or assessing needs. This is particularly relevant where one party is arguing that the marriage was short and contributions should be assessed more conservatively.

It also highlights why understanding the legal significance of how a relationship develops — before, during, and even after marriage — is so important when it comes to financial outcomes.