This is one of the most misunderstood parts of the whole child maintenance system, and it matters enormously to both sides. Paying parents are frequently told by colleagues that "pensions do not count". Receiving parents are frequently told that a sudden jump in pension contributions is something they can do nothing about. Both are wrong.
The short answer is that pension contributions do reduce the income the CMS assesses you on, and that is deliberate government policy rather than a loophole. But that reduction is not unlimited, and there is a specific legal route for the receiving parent to challenge contributions that look like they exist mainly to shrink a maintenance bill.
Why pension contributions reduce your assessment at all
The CMS calculates maintenance from your gross weekly income. Under the Child Support Maintenance Calculation Regulations 2012, that figure normally comes straight from HMRC for the latest tax year for which information is available. This is what the CMS calls your historic income.
The regulations then require the CMS to deduct the amount of any relievable pension contributions you make. "Relievable" is the key word. It means contributions that qualify for UK tax relief. The policy logic is straightforward: money you put into a pension is not money available to you now, and the state does not want to discourage people from saving for retirement simply because they are also paying maintenance.
So the sequence is:
- Start with gross annual income from HMRC
- Deduct relievable pension contributions
- Deduct an allowance for any relevant other children living with you
- Convert to a weekly figure and apply the percentage rate
- Apply any shared care reduction
Because the pension deduction happens near the top of that chain, it flows through everything below it. A pension contribution reduces the base your entire liability is built on.
The three scheme types, and why the difference is critical
This is where most of the confusion comes from. There are three ways UK pension contributions are administered, and the CMS sees them very differently.
1. Net pay arrangement (most workplace and occupational schemes)
Your contribution comes out of your pay before income tax is calculated. Your employer reports a lower taxable pay figure to HMRC through Real Time Information.
The practical effect is that the reduction is already baked into the figure the CMS receives. HMRC tells the CMS your taxable pay, and that number has already had your pension taken off it. You do not need to do anything. It happens automatically.
This is why some paying parents in occupational schemes find their assessment is lower than they expected and never work out why.
2. Salary sacrifice
Salary sacrifice goes further. You contractually give up part of your salary in return for your employer paying a larger amount into your pension. Your actual contractual gross salary is reduced.
Because your gross pay itself is lower, the figure HMRC holds is lower, and therefore the CMS assessment is lower. Salary sacrifice also reduces National Insurance for both you and your employer, which is why employers like it.
For CMS purposes salary sacrifice is the most effective of the three at reducing an assessment, because it reduces gross pay at source rather than being applied as a deduction afterwards. It is also, for exactly that reason, the arrangement most likely to attract a diversion of income challenge if the timing looks suspicious.
3. Relief at source (most personal and stakeholder pensions, and some workplace schemes)
You pay in from your take home pay. The pension provider claims 20 per cent basic rate relief from HMRC and adds it to your pot. Higher rate taxpayers claim the rest through Self Assessment.
Here is the problem. Your taxable pay reported to HMRC is unchanged. The pension contribution is invisible in the figure the CMS pulls. If you do nothing, you will be assessed on income you have already put into a pension.
Which type am I in?
| Clue | Likely scheme type | Do I need to tell the CMS? |
|---|---|---|
| Pension shown as a deduction on your payslip, and taxable pay is lower than gross pay | Net pay arrangement | No, it is automatic |
| Payslip shows a reduced gross salary and a separate employer pension line | Salary sacrifice | No, it is automatic |
| You pay a pension provider by direct debit from your bank account | Relief at source | Yes, you must tell them |
| You are self employed and pay into a SIPP or personal pension | Relief at source | Yes, you must tell them |
If you are not sure, look at your P60. Compare the "pay" figure to what you know your salary to be. If the P60 figure is already lower, your pension is coming off before HMRC sees it.
What the reduction is actually worth
Let us make this concrete. Take a paying parent earning £45,000 gross with one child, no shared care, no other children.
Weekly gross is roughly £865. That puts them into the basic plus band, so 12 per cent applies to the first £800 and 9 per cent to the amount above it.
| Pension contribution | Assessed gross annual income | Approximate weekly maintenance |
|---|---|---|
| None | £45,000 | £101.85 |
| 5 per cent (£2,250) | £42,750 | £98.65 |
| 10 per cent (£4,500) | £40,500 | £93.46 |
| 20 per cent (£9,000) | £36,000 | £83.08 |
So going from no pension to a 10 per cent contribution saves roughly £8 a week, around £435 a year. Going to 20 per cent saves roughly £19 a week. Meaningful, but notice the shape of it. You are giving up £9,000 of income to save £975 of maintenance. Nobody sensible funds a pension purely to reduce maintenance, which is precisely why modest and long standing contributions are rarely challenged.
You can model your own figures with our net pay child maintenance calculator.
Diversion of income: when the receiving parent can challenge it
This is the counterweight, and receiving parents are very often unaware it exists.
Under Regulation 71 of the Child Support Maintenance Calculation Regulations 2012, the receiving parent can apply for a variation on the ground of diversion of income. The test is whether the paying parent has the ability to control the amount of income they receive, and has unreasonably reduced that income by diverting it to some other person or for some other purpose.
Excessive pension contributions can fall squarely within this. The CMS is not obliged to accept every contribution at face value simply because it qualifies for tax relief.
What tends to make a contribution look like diversion
- Timing. A contribution rate that jumps immediately after a CMS application, an annual review, or notification of a change in circumstances.
- Scale. Contributing a very large share of income, particularly where it exceeds what the person could realistically live on, or where it far exceeds normal employer scheme rates.
- Control. Company directors and the self employed have direct control over contribution levels in a way an ordinary employee usually does not. That control is central to the Regulation 71 test.
- Lifestyle inconsistency. A declared income that does not plausibly support the paying parent's visible standard of living.
- Reversal. Contributions that drop back down once children age out of the calculation.
What usually does not
- Long standing contributions that predate the separation
- Auto enrolment minimums, currently 5 per cent employee and 3 per cent employer
- Standard employer scheme rates, including generous public sector schemes such as the NHS, teachers and civil service, where the rate is set by the scheme and not by the individual
- Contributions in line with what colleagues in the same role pay
What happens if a diversion variation succeeds
The CMS adds the diverted amount back into the paying parent's income and recalculates. The variation normally takes effect from the date of the application, not from when the diversion began, which is why applying promptly matters.
Salary sacrifice: the specific questions people ask
Does salary sacrifice reduce child maintenance?
Yes. Because it reduces contractual gross pay, the figure HMRC holds and passes to the CMS is lower. This applies to pension salary sacrifice and, in principle, to other salary sacrifice arrangements such as cycle to work schemes or electric car schemes, though the amounts involved are usually much smaller.
Can the CMS look through a salary sacrifice arrangement?
Yes, through the same diversion of income route. The fact that an arrangement is legitimate for tax purposes does not automatically make it acceptable for child support purposes. These are two different statutory tests.
What about an electric car through salary sacrifice?
A car scheme reduces your gross pay in exchange for a benefit you personally enjoy. That is a materially different picture from a pension contribution, where the money is genuinely locked away until retirement. Receiving parents challenging a car sacrifice generally have a stronger diversion argument than they would against a pension, because the paying parent is receiving something of immediate personal value.
Pension contributions if you are self employed or a company director
If you are self employed, contributions to a personal pension or SIPP are relief at source, so the CMS will not see them automatically. You need to declare them.
If you are a limited company director, employer contributions made by your company are a particularly sensitive area. The money never reaches you as personal income at all, so it does not appear in your HMRC figure. Combined with the level of control a director has, this is exactly the fact pattern Regulation 71 was designed for. It is entirely possible to make legitimate employer pension contributions as a director, but expect scrutiny if the amounts are large relative to what you draw. We cover this in more depth in our guide to child maintenance for limited company directors and our guide to child maintenance when you are self employed.
Practical steps
If you are the paying parent
- Work out which scheme type you are in using your payslip and P60.
- If it is relief at source, contact the CMS and provide contribution statements. Ask them to confirm in writing that the deduction has been applied.
- Check your annual review calculation each year to confirm the deduction is still being applied. It does sometimes drop off when a case is recalculated.
- If you believe the CMS has ignored evidence you supplied, you have one month from the decision to request a mandatory reconsideration.
If you are the receiving parent
- Ask the CMS for a breakdown of how the assessment was reached. You are entitled to know the gross income figure used, though not to see the other parent's payslips.
- Look at whether the contribution level changed around the time of the application or a review.
- If the pattern looks like diversion, apply for a variation. There is no fee and no penalty for an unsuccessful application.
- If the CMS refuses the variation and you disagree, request a mandatory reconsideration within one month, then appeal to the First tier Tribunal if needed.
Where this sits in the wider picture
It is worth keeping perspective. Pension contributions are one of a small number of legitimate reasons a CMS assessment can be lower than a receiving parent expects. The others are shared care, relevant other children in the paying parent's household, and the income bands themselves flattening out above £800 a week.
Equally, a paying parent saving properly for retirement while paying maintenance is doing something the system explicitly permits and encourages. The dividing line the law draws is not between saving and not saving. It is between saving and manufacturing a lower assessment.