Can the CMS Take Money From Your New Partner?

Two different questions get asked as if they were one. A paying parent moves in with a new partner and worries the assessment is about to jump. A couple opens a joint account and wonders whether the partner's wages are now within reach of the CMS.

The answers point in opposite directions. Your new partner's income can never increase your maintenance figure. Their money sitting in a joint account can be taken by an enforcement deduction order. No, and yes.

Part one: the calculation ignores your new partner entirely

The CMS works from one number. That number is the paying parent's gross annual income, taken directly from HMRC records. There is no box for household income. There is no stage where a caseworker adds a partner's salary to yours.

Your new partner's earnings are not counted. Neither are their savings, their property, their pension or anything else they own. If they earn £90,000 and you earn £24,000, your assessment is worked out on £24,000. If they own the house outright and you pay them rent, your assessment is still worked out on £24,000.

The myth persists because most of the rest of the benefits system does work on household income. Universal Credit, tax credits and council tax support all look at what a couple has coming in between them. Child maintenance does not. It sits on a different statutory footing, and the only income it measures is the income of the parent who owes the money.

The same applies in reverse. The receiving parent's new partner is ignored too. The formula does not look at either household. It looks at one person's taxable income. Our guide to what counts as income for child maintenance sets out exactly which figures the CMS can and cannot use.

The percentages apply to your income only

Moving in with someone who earns well does not push you up a band, because the band is set by what you personally earn. The five bands work like this.

Gross weekly income above £3,000 a week is ignored entirely by the formula. Our full walkthrough of how child maintenance is calculated covers each band, and the calculator will run your own figures.

The bit almost nobody knows: your partner's children can cut your bill

This is the genuinely useful part, and it is the opposite of what most people fear.

Before the maintenance percentage is applied, the CMS reduces your gross income to reflect other children living in your household. The reduction is:

• 11% for one other child in the household
• 14% for two
• 16% for three or more

Here is the point that gets missed. This includes the children of a new partner who live with you. They do not have to be biologically yours. If your partner moves in with two children, your assessable income drops by 14% before the maintenance percentage is worked out.

A worked example. Gross income of £40,000 a year, one qualifying child, nobody else in the household. That is £769.23 a week, so the basic rate applies at 12%, giving £92.31 a week. Now your partner and their two children move in. The 14% reduction comes off first, so the calculation runs on £34,400, or £661.54 a week. Twelve per cent of that is £79.38 a week. Roughly £672 a year lower, on identical earnings.

Part two: enforcement can reach a joint account

Now the answer flips, and this is where people get caught out.

Enforcement is not part of the assessment. It only begins once maintenance goes unpaid and arrears build up. At that stage the CMS has powers that reach further than the calculation ever does.

Before 2018, moving money into a joint account was an effective way of putting it out of reach. That loophole is closed. The Child Support (Miscellaneous Amendments) Regulations 2018 (SI 2018/1279) extended deduction orders to joint accounts, and to unlimited partnership and business accounts.

So money paid into an account held in two names is exposed to enforcement against the paying parent's arrears, even though the partner who paid it in owes the CMS nothing.

That is the reasoning behind the change. With £791.2 million of unpaid maintenance accumulated since 2012, the department wanted the account structure to stop being the deciding factor in whether a debt could be recovered. The effect on households is that a new partner can find themselves drawn into a debt that predates the relationship, purely because of where the wages land each month.

How the money gets split

The CMS does not simply assume the whole balance belongs to the paying parent. But the default is blunt. If it is not clear how much of the money belongs to whom, the amount is divided by the number of account holders. On a two person joint account, the starting assumption is a 50/50 split.

What every account holder can do about it

All account holders have the right to ask the CMS to review a decision to deduct from a joint or unlimited partnership account. That right belongs to the new partner personally, not only to the paying parent. In that review you can:

• Show how much each person actually contributes to the account
• Evidence it with wage credits, transfers and standing orders rather than assertion
• Explain, if it is a business account, how the business uses the money in it
• Ask the CMS to reconsider the share it has attributed to the paying parent

The purpose of the review is to establish what share is genuinely the paying parent's. If your partner pays in the whole salary and you contribute a fraction of the balance, say so and prove it, rather than accepting the automatic half.

A sole account in your partner's name is not at risk

This is worth stating plainly, because the fear runs well ahead of the facts. The CMS deduction powers follow the paying parent's liability. An account held solely in a new partner's name, with no connection to the paying parent, is not exposed to it. The exposure is specifically joint accounts and shared business accounts. That is a description of where the powers reach, not a suggestion to move money around once arrears exist.

How likely is any of this?

Real, but nowhere near routine. DWP official statistics with data to March 2026 give the scale.

Set 5,400 deduction orders against 810,000 arrangements and you are well under one per cent of cases. A deduction order is a serious step that the CMS has to work up to, not something that lands on a case that is being paid.

It also does not arrive out of nowhere. Arrears have to exist first, and the CMS has to have followed the proper process. Our guides to what happens if you do not pay child maintenance and what liability orders really are set out the sequence. If you want to know what is actually owed on your case, the arrears calculator breaks it down. Bear in mind that arrears never expire, so a balance from years ago can still be the trigger.

What a new partner should actually do

1. Stop worrying about the assessment. Your income is not in it and never will be. No amount of pay rise on your side changes the figure.
2. Check the household children reduction has been applied. If your children live in the household, that reduction should be in the calculation. It often is not, because nobody reported it.
3. Keep a paper trail on any joint account. Contribution records are exactly what a review of a deduction decision turns on, and they are much easier to produce as you go than to reconstruct later.
4. If a deduction letter arrives, respond in your own name. You are an account holder with your own right to ask for a review. Do not leave it to your partner.
5. Deal with arrears before enforcement starts. Everything on this page is avoidable at the arrears stage.

Two questions, two answers

This article is information, not legal advice. If a deduction order has been made against an account you hold, or you are dealing with arrears you dispute, get advice on your own circumstances from a solicitor or from Citizens Advice.