Child Maintenance Calculator (Self-Employed)
Calculate CMS child maintenance for self-employed paying parents using HMRC income rules. Updated 2026.
Last updated: March 2026
CMS Child Maintenance Calculator — Self-Employed 2026
Enter self-employed net profit and shared care nights to calculate weekly and monthly maintenance
Income Details
Children & Shared Care
CMS Basic Rates 2026 — Quick Reference
| Qualifying Children | Weekly Gross Income | Rate |
|---|---|---|
| 1 child | £100.01–£3,000 | 12% |
| 2 children | £100.01–£3,000 | 16% |
| 3+ children | £100.01–£3,000 | 19% |
| Any | £100 or under | £8.80/week flat rate |
| Any | £3,001–£3,200 | Standard rate + 9/12/15% |
Expert Guide: Child Maintenance for Self-Employed Parents
1. How the CMS Calculates Income for Self-Employed Parents
The Child Maintenance Service (CMS) operates under the Child Support Act 1991 and the Child Support (Maintenance Calculations and Special Cases) Regulations 2000 (as amended). For employed parents, gross income is straightforward — HMRC provides the earnings figure. For self-employed parents, the process is more complex.
The CMS income figure for self-employed parents is gross income = net profit from self-employment as reported to HMRC on the self-assessment tax return. The CMS contacts HMRC to verify this figure. They typically use the most recent annual return submitted. If the latest year's return has not yet been filed, they may use the previous year's figure or an estimate provided by the paying parent (which is subsequently adjusted when the actual return is filed).
For limited company directors: The CMS uses total taxable income including: salary drawn from the company AND dividends received. Retained profits left in the company are NOT counted in the standard assessment — but see the variation rules below, which address this situation.
Pension contributions: Approved pension contributions (qualifying pension scheme contributions) can be deducted from gross income for the purposes of the CMS calculation. This is one of the few allowable deductions. Contributions to a personal pension or employer scheme are deducted from the gross figure, reducing the maintenance liability.
Tax paid is not deducted — unlike the old child support regime, the current CMS uses gross income, not net income. Income tax, National Insurance, and VAT are not deducted from the calculation.
2. The CMS Rate Calculation — Step by Step
Step 1: Establish annual gross income
Total = self-employment net profit + dividends + other taxable income − qualifying pension contributions. This gives the annual gross income figure.
Step 2: Calculate weekly gross income
Weekly gross income = Annual gross income ÷ 52
Step 3: Adjustment for other children in household
If the paying parent has other children living with them (not qualifying children of the maintenance assessment), their gross weekly income is reduced before applying the rate: 1 child in household: reduce gross income by 11%; 2 children: reduce by 14%; 3+: reduce by 16%.
Step 4: Apply the basic rate
1 qualifying child: 12% of adjusted weekly gross income. 2 qualifying children: 16%. 3 or more: 19%. This gives the weekly maintenance amount.
Step 5: Apply shared care reduction
- Under 52 nights/year: no reduction
- 52–103 nights: divide maintenance by 7, multiply by 6 (reduce by 1/7)
- 104–155 nights: reduce by 2/7
- 156–175 nights: reduce by 3/7
- 176+ nights: halve the amount, then subtract £8.80 per week
Step 6: Convert to monthly amount
Monthly maintenance = weekly amount × 52 ÷ 12
3. Variation Applications — Challenging the Standard Assessment
Either the paying parent or the receiving parent can apply for a variation to adjust the standard assessment. For self-employed paying parents, variations are particularly important because the standard assessment based on last year's net profit may significantly overstate or understate current income.
Grounds for variation that INCREASE maintenance (receiving parent applies):
- Assets variation: The paying parent has assets with a total value exceeding £31,250 (excluding their pension, main home, and business assets to some extent). The CMS adds a notional income of 8% per year on excess assets to the gross income figure.
- Lifestyle inconsistency: The paying parent's lifestyle (property, cars, holidays, spending) is inconsistent with their declared income. The CMS can investigate and attribute a higher income.
- Diversion of income: The paying parent is diverting income to a third party (e.g. a new partner, a connected business, a family trust) to reduce their assessable income artificially.
- Income not included: Income from property, trusts, or other sources not captured in the standard assessment.
Grounds for variation that DECREASE maintenance (paying parent applies):
- Special expenses: Costs for travelling to maintain contact with the qualifying child; costs of supporting a child with a disability; boarding school fees paid by the paying parent for the qualifying child; debts incurred for the family's joint benefit during the relationship.
- Payments under previous court orders (pre-CMS arrangements) may be deducted in limited circumstances.
The CMS can request bank statements, business accounts, HMRC records, and lifestyle evidence when investigating a variation application. Deliberate income suppression is a serious matter — the CMS has powers to refer cases to the Compliance and Arrears Service (CAS) for more intensive enforcement.
4. Income Fluctuation — Requesting a Review
The standard CMS assessment is based on the most recent HMRC tax return, which by definition reflects the prior year's income. For self-employed parents whose income fluctuates significantly year to year, this can create substantial over- or under-payment problems.
Annual review: The CMS automatically reviews the assessment once a year and adjusts it based on the new HMRC income data. There is typically a lag of several months between the end of the tax year and the assessment being updated.
Change of circumstances review: Either party can request a review at any time if the paying parent's gross income has changed by 25% or more since the last assessment. For a self-employed parent whose business has had a very bad year, this can significantly reduce the liability. Conversely, if income has increased substantially, the receiving parent can request an upward review.
In-year estimates: If the paying parent has not yet filed their self-assessment return (e.g. they are early in the new tax year), the CMS may accept an estimate of current-year income, which is later reconciled against the actual return. Providing a materially false estimate is a criminal offence.
Application via GOV.UK: Change of circumstances reviews can be requested online through the CMS portal (CMS Online), by phone (0800 171 2345), or in writing. Always keep records of all correspondence with the CMS.
5. Direct Pay vs Collect and Pay — Choosing the Right Arrangement
Once the CMS has calculated the maintenance amount, the parties can choose how payments are made:
Direct Pay (formerly "Family Based Arrangement"): The paying parent pays the receiving parent directly — by bank transfer, standing order, or other agreed method. The CMS does not handle the money. There is no CMS collection fee. Both parties must agree to Direct Pay. If either party is uncomfortable or there is a history of non-payment, Direct Pay may not be appropriate.
Collect and Pay: The CMS collects payment from the paying parent and forwards it to the receiving parent. The CMS charges a collection fee: 20% added to the amount the paying parent must pay (e.g. £100/week maintenance becomes £120/week), and 4% deducted from the amount received by the receiving parent. This incentivises both parties to use Direct Pay where possible.
For self-employed paying parents, Direct Pay is common — there is no employer from whom payments can be deducted automatically. If the paying parent defaults on Direct Pay, the receiving parent can ask the CMS to switch to Collect and Pay (with the associated charges). The CMS can then use enforcement mechanisms to collect arrears.
6. Dividend Income and Company Directors — The Key Issues
One of the most common disputes in CMS assessments involves limited company directors who minimise their salary and take most of their remuneration as dividends. Under the current CMS rules, dividends reported on the self-assessment tax return are included in the gross income calculation.
The retained profits problem: If a director retains profits in the company (as company reserves) rather than drawing dividends, those profits are not counted in the standard assessment. Only income actually extracted (salary + dividends) is included. This creates an incentive for paying parents to suppress their extracted income by leaving money in the company.
Lifestyle inconsistency variation: If the receiving parent believes the paying parent is retaining profits in the company to artificially reduce the CMS assessment, they can apply for a variation on lifestyle inconsistency grounds. The CMS investigator will look at the paying parent's actual expenditure (property, cars, holidays, credit card spending) and compare it against the declared income. If there is a significant gap, the CMS can attribute additional income.
Company asset variation: If the company has significant assets (and is effectively a vehicle for personal wealth accumulation), the assets variation may apply. The CMS assesses whether the company's assets exceed the £31,250 threshold (after deducting business-necessary assets), and if so, attributes notional income to the paying parent based on those assets.
Limited company directors involved in CMS disputes are strongly advised to seek specialist legal and financial advice. The CMS has powers to request business accounts and information from Companies House and HMRC.
7. CMS Appeals and Mandatory Reconsideration
If either party disagrees with a CMS decision (including the income figure used, the calculation, or a variation decision), the appeal process is:
Step 1 — Mandatory Reconsideration (MR): Either party must apply for a Mandatory Reconsideration within one month of the CMS decision. The CMS sends the case to a different caseworker for review. The MR can overturn, modify, or uphold the original decision. If the decision is upheld, a Mandatory Reconsideration Notice is issued.
Step 2 — First-Tier Tribunal (Social Entitlement Chamber): If unsatisfied with the MR outcome, either party can appeal to the Social Security and Child Support Tribunal within one month of the MR Notice. This is a formal hearing before an independent tribunal. Most cases are resolved on the papers (written representations), but oral hearings are available. The tribunal can substitute its own decision for the CMS decision. Representation by a solicitor is helpful but not required — many parties represent themselves.
Step 3 — Upper Tribunal: An appeal from the First-Tier Tribunal can only be made on a point of law (not a disagreement with the factual findings). Permission is required. Very few cases reach this stage.
Common grounds for appeal: CMS used the wrong income figure; failed to apply a variation correctly; made an arithmetic error; did not properly assess shared care nights; applied incorrect rates.
Common Child Maintenance Mistakes for Self-Employed Parents
1. Not Disclosing Dividend Income — CMS Can Find Out
Some self-employed parents who operate through limited companies deliberately omit dividend income from the CMS income figure, declaring only their salary. This is a mistake. The CMS has direct access to HMRC data, which includes all self-assessment income including dividends. Providing false information to the CMS is a criminal offence under the Child Support Act 1991 and can result in a fine or prosecution in addition to recalculated arrears.
Even where the CMS initial assessment misses dividend income, the receiving parent can apply for a variation, and the CMS will obtain the full self-assessment data directly from HMRC. Any arrears arising from undisclosed income are backdated to the date of the original assessment.
2. Not Requesting a Review When Income Falls Sharply
Self-employed income can fall dramatically — a bad trading year, business loss, illness, or market change can reduce income by 50% or more. If the CMS assessment is based on last year's higher income, the paying parent may be paying significantly more than they should while their current financial position is dire.
Many paying parents are unaware that they can request a change of circumstances review immediately when their income falls by 25% or more. The review adjusts the assessment from the date of the review request (not retrospectively). Every month of delay costs money. If your income has fallen sharply, request a CMS review as a matter of urgency.
3. Not Counting Overnight Stays Correctly — Missing the Threshold
The shared care reduction only kicks in at 52 or more nights per year. Many paying parents who have the child for 40–50 nights per year are just below this threshold and receive no reduction at all. Conversely, moving from 51 nights to 52 nights triggers a one-seventh reduction — worth hundreds of pounds annually.
Keep a diary or calendar of all overnight stays. The CMS counts nights the child sleeps at the paying parent's home; daytime visits do not count. Where shared care arrangements are informal and undocumented, disputes can arise. If you believe you are entitled to a shared care reduction, document every overnight stay and be prepared to provide evidence (school diaries, social media, receipts for activities) if the receiving parent disputes the number of nights.
Official CMS Resources
GOV.UK — Official CMS Calculator
The official Child Maintenance Service calculator on GOV.UK gives an indicative figure based on the same formula used by the CMS. Always verify your estimate here before applying to the CMS.
GOV.UK — Apply to the CMS
How to apply to the Child Maintenance Service, what information you need, fees, and what happens during the assessment process. Includes information on variations and reviews.
GOV.UK — Appeal a CMS Decision
Step-by-step guidance on requesting mandatory reconsideration and appealing to the Social Security and Child Support Tribunal if you disagree with a CMS assessment or variation decision.
Related Calculators
Expert Reviewed — This calculator uses the current CMS 2012 scheme rates. Rates are periodically updated by the DWP. Last verified: March 2026.
People Also Ask
Worked Examples: Child Maintenance for Self-Employed
Example 1: Sole Trader, 2 Children, No Shared Care
Self-employed plumber with net profit of £52,000/year. 2 qualifying children. No overnight stays.
- Gross weekly income: £52,000 ÷ 52 = £1,000/week
- No household children adjustment needed (0 other children)
- Rate for 2 children: 16%
- Weekly maintenance: £1,000 × 16% = £160/week
- Monthly maintenance: £160 × 52 ÷ 12 = £693/month
Example 2: Limited Company Director, 1 Child, 104 Nights Shared Care
Director with salary of £12,570 + dividends of £48,000 = £60,570 total annual income. 1 qualifying child. 104 overnight stays per year.
- Gross weekly income: £60,570 ÷ 52 = £1,165/week
- Rate for 1 child: 12%
- Weekly maintenance (before shared care): £1,165 × 12% = £139.80/week
- Shared care reduction (104–155 nights = 2/7 reduction): £139.80 × (1 − 2/7) = £139.80 × 0.714 = £99.82/week
- Monthly maintenance: £99.82 × 52 ÷ 12 = £432/month
Disclaimer: These examples illustrate the CMS formula. Always verify using the official GOV.UK CMS calculator. Income used by the CMS comes directly from HMRC and may differ from self-reported figures.