Child Maintenance Service UK 2025: How Your Payments Are Calculated

The Child Maintenance Service replaced the Child Support Agency in 2012 and is the government body responsible for calculating and in some cases collecting child maintenance payments between separated parents in the UK. Understanding how the CMS works, how it calculates payments, and what options exist for both paying and receiving parents helps you navigate the system more effectively and ensures children receive the financial support they are entitled to.

This guide explains the CMS calculation methodology for 2025, covering income assessment, shared care deductions, variations, the collection options available, and what happens when payments are not made. Our child maintenance calculator lets you estimate what payments should be under the current CMS rules before making a formal application.

How CMS calculates the basic rate

The CMS uses the paying parent's gross weekly income as the starting point for calculation. This gross income figure is obtained from HMRC records, typically using the most recent tax year's data. The income used is before tax and NI deductions but before pension contributions, which is a distinction that matters for anyone making significant pension contributions because the calculation uses gross income rather than net.

For paying parents in the basic rate band, the percentage applied depends on the number of qualifying children. The rate is 12% of gross weekly income for one child, 16% for two children, and 19% for three or more children. This percentage is applied to gross income between £800 and £3,000 per week. Weekly gross income above £3,000 attracts a lower additional rate of 9%, 12%, or 15% depending on the number of children, applied to the income above £3,000 per week up to a maximum of £800 per week of additional income considered.

How income is assessed for CMS purposes

The CMS uses HMRC data to verify the paying parent's income. For employed individuals, this is typically the gross annual income from the most recent full tax year converted to a weekly figure. The income includes employment income, self-employment income, rental income, pension income, and most other taxable income. Income from pensions in payment, taxable benefits, and some investment income is included.

Self-employed paying parents are assessed on their gross profit from self-employment as reported to HMRC. This is a point of frequent dispute because self-employed income can vary significantly year to year, and high business expenses can reduce the profit figure. If the CMS income figure is based on a year with atypically low income, the receiving parent can apply for a variation if the current year's income is significantly higher. Similarly, a paying parent whose income has genuinely reduced since the reference year can request a reassessment.

Pension contributions are not deducted from the gross income figure used by the CMS. This is different from how pension contributions affect income tax calculations, and it sometimes surprises paying parents who make large pension contributions and assume they reduce their CMS assessment. They do not. The only way pension contributions affect the CMS calculation is indirectly through reducing taxable income shown on the tax return in future years.

Shared care deductions

If the paying parent has the children staying overnight, the CMS applies a deduction to the maintenance calculation based on the number of nights per year. This recognises that the paying parent bears direct costs during the nights the children are with them. The deduction is applied as a reduction to the maintenance amount and uses specific thresholds based on average nights per week.

If the paying parent and receiving parent are sharing care more or less equally, the calculation adjusts so that the parent with the higher income pays a reduced amount to the parent with the lower income. The equal split calculation uses the formula for each parent as if they were the paying parent and the difference determines what flows between them.

Variations: when the standard calculation can be changed

Either parent can apply to the CMS for a variation from the standard calculation in certain circumstances. The paying parent can apply for a variation if they have costs that the standard calculation does not account for, such as costs of maintaining contact with the children, debts taken out for the benefit of the family before separation, or boarding school fees that reduce disposable income. The receiving parent can apply for a variation if they believe the paying parent has additional income not captured by the standard assessment, such as investment income, diversion of income through a company, or lifestyle that exceeds what declared income would support.

The variations process adds complexity and often contention to CMS cases. The CMS has the power to request detailed financial information from paying parents and can involve HMRC in investigations where income concealment is suspected. For self-employed paying parents in particular, the variations process is frequently used by receiving parents who believe that declared profits understate actual income.

Direct Pay vs Collect and Pay

Once the CMS has calculated the maintenance amount, parents can choose how payments are managed. Direct Pay means the paying parent pays directly to the receiving parent according to the CMS schedule, with CMS providing the framework but not handling money. This avoids service charges and is appropriate where the relationship between parents allows for a degree of co-operation.

Collect and Pay means the CMS collects payments from the paying parent and passes them to the receiving parent. This service carries additional charges. The paying parent pays a 20% surcharge on top of the maintenance amount, and the receiving parent receives 4% less than the calculated amount. These charges are significant and amount to a meaningful reduction in what the child actually receives compared to Direct Pay, which is why CMS encourages Direct Pay wherever possible.

Enforcement when payments are not made

The CMS has substantial enforcement powers when paying parents do not meet their obligations. These include deduction from earnings orders sent directly to employers, deductions from bank accounts, collection of debt from lump sum payments such as pensions or property proceeds, orders to deduct from investments, driving licence revocation, passport confiscation, and ultimately committal to prison for persistent non-payment. The enforcement regime is considerably stronger than under the old CSA.

Arrears can be pursued for as long as they exist, and the CMS charges interest on arrears as well as the collection service charges. If you are falling behind on payments, engaging with the CMS proactively to discuss a payment plan is strongly preferable to waiting for enforcement action. Our child maintenance calculator helps you understand the calculated amount in advance, and if you are struggling financially, our salary calculator can help you review your overall income and tax position.