In many cases particularly where there are young children, maintenance is payable to the wife as part of the divorce settlement until she remarries, dies or “further order”. If the wife subsequently moves in (cohabits) with a new partner this is likely to result in her ex-husband applying to vary the maintenance order under section 31 of the Matrimonial Causes Act 1973. The maintenance can be increased or decreased on variation and can also be capitalised to enable a clean break to take place. This would involve the husband paying the ex-wife a lump sum in exchange for termination of her maintenance claim.
Cohabitation counts as one of the circumstances of the case which would be looked at under section 21(1) of the Matrimonial Causes Act 1973 but it does not have any greater importance than any of the other factors. It can often be very difficult for ex-husbands to accept that their ex-wife’s cohabitation does not automatically disentitle her from receiving maintenance under the court order.
The 1995 case of Atkinson v Atkinson established that when assessing the relevance of a wife’s cohabitation it was important to consider the financial circumstances of the wife’s cohabitee and “his capacity to make a reasonable contribution in return for the benefits of the provision of a home”. Later, in the 2003 case of Fleming v Fleming  EWCA Civ 1841 the Court of Appeal stated that cohabitation should not be equated with marriage even though society’s attitudes had changed. It also stated that in a case where there had been lengthy cohabitation the range of discretion held by the judge allowed the court to place considerable weight on that factor.
More recently in the case of AB v CB  EWH C2998 (Fam) Mostyn J warned wives of the potential legal difficulties arising from entering into new relationships before their financial settlements on divorce are sorted out. In this case, the parties were married for 10 years and had 2 adopted children. In 2005 they moved into a farmhouse owned by the husband’s wealthy family. In 2009 a trust was set up in respect of the farmhouse, the principal beneficiary of which was the husband and the main discretionary beneficiaries the children. After the trust was established the parties spent funds on refurbishing the property. In 2012 the marriage broke down and the wife (who was a journalist) went to live with her parents, the husband remaining in the farmhouse where he lived with his new partner. Mostyn J found that the wife knew it was intended that the farmhouse would stay in the husband’s family and after it had been used by them it would revert to the family estate. The wife did not disclose the fact that she had a new relationship and this was only discovered by “investigations” by the husband’s lawyers. The wife claimed that nonetheless, she had no intention of cohabiting. She was awarded £23,000 from the trust outright (in respect of her contributions) and £134,000 on the terms of a life tenancy. In his judgment, Mostyn J stated “Relationships like this always are a significant fly in the ointment in the assessment of needs. One cannot make assumptions if it is not a full-blown cohabitation akin to marriage, that it will grow into that, because if it does not, the wife may be left stranded between Scylla v Charybdis if the assumption is wrongly made. On the other hand, if one makes a needs assessment on the basis she is a single woman and she soon cohabits, then the paying party….. can rightfully feel significantly aggrieved”.
Taking all the facts into account the judge concluded that £250,000 would be enough to meet the wife’s needs stating that he could not “ignore the existence of her relationship”.
The Court of Appeal has recently considered Mostyn J’s decision in the case of Hart v Hart  EWCA Civ 497. In his judgment Munby LJ found that Mostyn J’s judgment in AB v CB does not lay down any principle of law and that these matters are “quintessentially matters of fact where the trial judge has to have regard to the totality of the evidence, including the nuance of that evidence, before coming to a conclusion as to whether the prospects of remarriage or indeed the future prospects of the relationship, should or should not, and if they should to what extent they should, be taken into account.”
In conclusion, it is clear that if a spouse or civil partner is found to be cohabiting the existence of that relationship will not be ignored even if no financial support is being provided by the cohabitee. The case law shows that the court’s approach is to focus on what the cohabitee should be contributing rather than his or her actual contribution. This is obviously a factor which anyone in receipt of maintenance under a maintenance order needs to take into account before moving in with a new partner.