Offsetting Mortgage Payments against CMS Assessment

It is a very common scenario - A and B buy a house together and each pays half the mortgage. They have children, then their relationship breaks down and A moves out. Does A have to carry on paying the mortgage?

If A moves out s/he will be expected to pay maintenance for the children either assessed by CMS or more usually at a rate A and B agree between them, often using the child support calculator on the gov.uk website. But does A have to pay half the mortgage as well?

The answer to this very straight forward question has been unclear until quite recently. That may seem surprising, but Child Support Regulations are remarkably complicated and there are relatively few reported cases on the subject, so it does not attract a lot of discussion amongst lawyers generally. But there seemed to be a direct conflict between two parts of the regulations on this particular point, where A remains on the mortgage and a part owner of the house.

A recent decision of the Upper Tribunal* has clarified that the answer is ‘no’ because A can apply to CMS to reduce his maintenance assessment by the amount of his contribution to the mortgage instalments i.e. offsetting one against the other. The guidance on CMS website said the opposite, but I expect it will soon be changed.

Judge Kate Marcus KC considered the regulations carefully and decided that, on a correct reading of them, the mortgage payments can fall within the definition of a “special expense” which A can ask the CMS to offset against the CMS assessment, even though A remains a part owner of the house. The amount of the reduction is discretionary, so it remains to be seen whether CMS will reduce the maintenance assessment by the whole of their share of or only part of it.  But on the whole the CMS approach to special expenses seems to be “all or nothing”.

Technically this only applies where A has been assessed by CMS, but A and B should probably bear it in mind when they are discussing an agreement between themselves.

As far as the mortgage lender is concerned, of course, A and B are what lawyers call ‘jointly and severally liable’ for the mortgage instalments so the lender can ask either or both of them to pay. The lender does not have to become involved in any argument between A and B about which of them is responsible. Many lenders are sympathetic to financial stress caused by relationship breakdown, and they may offer some flexibility or help if they are asked. But the help is usually temporary and, in the end, if the instalments are not paid the lender will take steps to enforce which could eventually mean the house gets repossessed.

In the longer term if B remains at the house, either as part of a divorce settlement or, if A and B are not married, as part of a postponed sale arrangement (under Trusts of Land and Appointment of Trustees Act 1996 or Schedule 1 Children Act 1989) B will be expected to pay the mortgage instalments as part of B’s housing costs. A will usually be paying rent or mortgage on a new home.

*8LM v SSWP & NM [2024] UKUT 259 (AAC) in September 2024

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Health Warning :This post is intended as a general guide only – and is correct as at April 2025. It is important to obtain expert advice about your own situation, I can certainly accept no responsibility for any loss you might suffer as a result of relying purely on the information on this website.

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John Pratley is an expert divorce lawyer, who has more than 25 years’ experience advising clients purely about divorce and related family law issues, such as the financial consequences of separating and divorcing. After establishing the first niche family law practice in Bristol, and going on to senior management roles in a national firm, John set up Apple Tree Family Law in 2018. Apple Tree Family Law solicitors specialise in advice about divorce and financial issues.

We are based in Bristol and Exeter, but we have clients all over the UK and further afield. We offer, simply, clear and accurate advice about divorce and family law issues, and the very best client service, for a clear and reasonable price.