Current CMS Income Assessment Rules
The current DWP guide was updated on 1 April 2026, while the Child Maintenance Decision Makers' Guide was updated on 29 May 2026. These are the most useful official starting points for checking an income calculation.
Historic Income: Latest Available Complete Tax Year
DWP says CMS normally obtains the Paying Parent's gross annual income from information supplied to HMRC by the Paying Parent, employer or another party such as an accountant.
CMS says it uses the latest available information for a complete tax year and tells both parents which tax year has been used.
Official Step 1 income guidanceWhat “Gross Annual Income” Means
Current DWP guidance defines the starting figure as yearly income before Income Tax and National Insurance, but after occupational or personal pension scheme contributions are taken away.
It can include employment earnings, self-employment profits, occupational or personal pensions and certain taxable benefits.
Gross income definitionAnnual-to-Weekly Formula Confirmed
DWP's current guide confirms that, after relevant pension/variation adjustments, CMS converts annual gross income to a weekly amount by dividing by 365 and multiplying by 7.
Current Income Normally Needs a 25% Difference
If a parent disputes the HMRC historic-income figure and supplies a current gross-income figure, DWP says CMS will only use it where it is at least 25% more or 25% less than the HMRC figure.
The change should also be permanent or long-term, not merely a short temporary fluctuation.
25% current-income rulePeriodic Current Income Checks Exist
Where CMS is already using a current-income figure supplied by the Paying Parent, employer or another party, DWP carries out a separate periodic current income check. It compares up-to-date current income with the latest HMRC figure and again applies the 25% test.
Annual & periodic review guidanceRTI Does Not Mean Automatic Recalculation Every Payday
HMRC's PAYE systems receive employer payroll information through Real Time Information, and DWP can use more recent evidence when establishing current income. But the statutory CMS scheme does not simply replace the maintenance calculation after every weekly or monthly payroll change.
The decisive questions remain whether CMS is using historic or current income, what evidence is available, and whether the statutory 25%/current-income conditions are met.
CMDMG maintenance calculationsVariable Earnings Are Still Annualised
For agency, commission, seasonal and other fluctuating earnings, a week with unusually low income does not by itself replace the statutory annual-income figure. The CMS framework is designed around an annual gross-income figure converted to a weekly average.
If the parent's underlying ongoing income has materially changed by at least 25%, current-income rules may become relevant.
Official calculation methodSelf-Employment: Taxable Profit Is Not Turnover or Drawings
DWP describes self-employment income as profits from a business. Turnover, money sitting in the business and personal drawings are not interchangeable with the taxable profit figure used for CMS.
The 2026 Upper Tribunal has also confirmed that a self-employed business loss cannot simply be offset against separate employment income when calculating CMS income.
2026 Upper Tribunal income decisionCompany Directors: Salary, Dividends and Diversion Need Separate Analysis
Director cases can be more complex because the main calculation and variation rules treat different income streams differently. Dividends and other unearned income can be considered through a variation where the statutory threshold is met, and diversion-of-income rules can apply where income is controlled or redirected so that it is excluded from the ordinary calculation.
Official additional-income variation guidance Upper Tribunal: historic/current income & dividendsAdditional Income Variation Thresholds
Current DWP guidance permits a variation for unearned income such as rental income, interest and dividends where it is at least £2,500 a year; notional income from qualifying assets worth at least £31,250; certain earned income of at least £100 a week in flat-rate cases; and diversion of income.
Variation categoriesCMS Normally Caps Gross Weekly Income at £3,000
Current guidance says the most gross weekly income CMS normally takes into account is £3,000. If income is higher, the Receiving Parent may be able to apply to court for additional child maintenance.
Current income bandsThe Weekly Income Figure Is Only the Start
After income is established, CMS applies the relevant Nil, Flat, Reduced, Basic or Basic Plus rate; takes account of relevant other children/family-based arrangements; then applies shared-care reductions where appropriate.
Full six-step calculationIf CMS Has Used the Wrong Income: Evidence Route
Build the challenge around the statutory income rule rather than only around current cashflow.
Important: “Current Income Review” Is Useful Shorthand, but the Legal Test Matters
The legislation and DWP guidance distinguish historic income and current income. A request for CMS to look at current earnings does not automatically mean the calculation changes. The evidence must fit the statutory current-income conditions, including the 25% test in the ordinary case.
Important: Affordability and the Income Calculation Are Not the Same Question
Rent, utilities, debt repayments and other living costs can be important when discussing hardship, arrears and enforcement arrangements, but they do not generally alter the statutory gross-income calculation simply because disposable income is low. Calculation changes must come through the statutory income, pension, other-child, shared-care or variation rules. The 60% protected-earnings rule is specifically a safeguard for a Deduction from Earnings Order, not a general cap on CMS liability.
DEO protected earnings ↗Official Income Assessment Sources
Income Assessment and Calculation Framework
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Child Maintenance Service (CMS)
Income Assessment and Calculation Framework
Understanding How CMS Calculates Gross Weekly Income, Uses Historic and Real-Time Earnings Data, and Deals with Income Fluctuations
Public Information Report
November 2025 Executive Summary
The Child Maintenance Service (CMS) uses a statutory formula to calculate child maintenance.
The starting point for almost every calculation is the paying parent's gross weekly income.
The figure used is usually obtained directly from HM Revenue & Customs (HMRC) and is generally based on income information from the most recently completed tax year. However, where income changes significantly, CMS may use more recent earnings information through a process known as a Current Income Review.
This report explains:
- How annual income is converted into weekly income.
- The difference between historic and current income assessments.
- How fluctuations in earnings affect maintenance.
- Why maintenance amounts sometimes appear disconnected from a parent's actual financial circumstances.
- The rights available to parents when calculations appear inaccurate.
1. The Starting Point: Gross Annual Income
CMS normally receives income information directly from HMRC.
This information may include:
- Employment earnings (PAYE)
- Self-employment profits
- Pension income
- Certain taxable benefits
- Taxable property income
- Other taxable sources declared to HMRC
The income figure supplied is usually based on the most recently available tax year rather than current earnings.
For example:
Tax Year Income
Annual Gross Income
2024/25
£39,000
CMS initially uses this figure even if the parent's circumstances have since changed.
2. Converting Annual Income to Gross Weekly Income
CMS legislation requires income to be expressed as a weekly figure.
The conversion formula is simple:
Gross Annual Income ÷ 365 × 7
or
Gross Annual Income ÷ 52.142857
Example
Annual income:
£39,000
Calculation:
£39,000 ÷ 365 = £106.85 per day
£106.85 × 7 = £747.95 gross weekly income
CMS would therefore assess the parent on approximately:
£748 per week
This weekly figure becomes the basis for maintenance calculations.
3. Why CMS Uses Historic Income
The child maintenance scheme was designed to provide consistency and administrative simplicity.
HMRC tax records are:
- Verified
- Auditable
- Available nationally
- Difficult to manipulate
Using tax-year income allows CMS to produce calculations quickly without requiring extensive investigation into a parent's current circumstances.
However, this approach can create problems where income has changed significantly since the relevant tax year.
4. Real-Time Income Information (RTI)
Employers submit earnings information to HMRC through the Real Time Information (RTI) system whenever employees are paid.
RTI records can show:
- Current salary
- Monthly earnings
- Reduced hours
- Sick pay
- Statutory payments
- Employment termination
CMS can access more recent income information when reviewing a case.
However, CMS does not automatically recalculate maintenance every time earnings change.
Instead, the historic HMRC figure remains in place until a review is triggered.
5. Current Income Reviews
A current income review may be requested when a parent believes the historic income figure no longer reflects reality.
Examples include:
Income Reduction
- Job loss
- Redundancy
- Reduced hours
- Long-term illness
- Business downturn
- Retirement
Income Increase
- Promotion
- Significant pay rise
- New employment
- Increased business profits
CMS may request evidence such as:
- Payslips
- Employment contracts
- P60s
- Accounts
- Tax returns
- Universal Credit statements
6. The 25% Change Rule
One of the most important rules in the CMS scheme is the 25% threshold.
Generally, CMS will only replace historic income with current income if the difference is at least 25%.
Example
Historic HMRC income:
£40,000
25% reduction threshold:
£30,000
If current income falls to:
£32,000
CMS may continue using the historic £40,000 figure.
If current income falls to:
£29,000
CMS may be required to reassess using current income.
This rule was introduced to reduce constant recalculations resulting from normal earnings fluctuations.
7. Fluctuating Income
Many people do not earn a fixed salary.
Examples include:
- Self-employed workers
- Contractors
- Commission-based employees
- Agency workers
- Seasonal workers
- Company directors
In these situations income can vary significantly throughout the year.
CMS generally focuses on annual income rather than monthly fluctuations.
Consequently:
A parent earning £5,000 one month and £1,500 the next may still be assessed using annual averages.
This can create periods where maintenance appears unaffordable despite the annual income assessment remaining unchanged.
8. Self-Employment and Company Directors
For self-employed individuals, CMS usually relies on HMRC taxable profit figures.
This can create differences between:
- Business turnover
- Business cash flow
- Personal drawings
- Taxable profit
Similarly, company directors may receive income through:
- Salary
- Dividends
- Retained profits
Parents sometimes argue that the HMRC figure does not accurately represent the money available to meet maintenance payments.
CMS has powers to investigate certain arrangements where income appears artificially reduced or diverted.
9. Shared Care Impact
Once gross weekly income has been established, CMS applies the statutory maintenance percentage.
After that, shared care reductions are applied.
The more overnight care provided by the paying parent, the greater the reduction.
This means two parents with identical incomes can pay very different amounts depending on overnight care arrangements.
10. Why Maintenance Can Seem Too High
Many complaints arise because maintenance is based on historic earnings rather than current affordability.
Common examples include:
- Income dropped after redundancy.
- Business profits collapsed.
- Illness reduced earnings.
- Cost of living increased significantly.
- Debt repayments increased.
- Housing costs increased.
Parents often discover that maintenance continues to reflect a previous year's income long after circumstances have changed.
11. Protected Earnings and Affordability
CMS legislation recognises that enforcement action should not leave a parent unable to meet essential living expenses.
Protected earnings provisions exist to ensure:
- Basic living costs can be met.
- Housing costs are considered.
- Enforcement remains proportionate.
Although child maintenance takes priority over many other financial commitments, CMS must still act reasonably when arranging collection and enforcement.
12. Public Concerns About the System
The most common criticisms of the current system include:
Historic Income Delays
Maintenance often reflects earnings from a period that may be 12–24 months old.
Rapid Income Changes
Parents experiencing sudden income reductions can struggle before reviews are completed.
Self-Employment Complexity
Business income can be difficult to assess fairly.
Affordability Concerns
Some parents argue that calculations do not adequately reflect actual disposable income.
Administrative Delays
Reviews and reconsiderations can take months to conclude.
13. Practical Advice for Parents
If your income has changed significantly:
- 1. Notify CMS immediately.
- 2. Request a current income review.
- 3. Keep evidence of all earnings.
- 4. Retain bank statements and payslips.
- 5. Record shared care arrangements accurately.
- 6. Request written explanations of calculations.
- 7. Challenge decisions through Mandatory Reconsideration where appropriate.
- 8. Escalate complaints if affordability concerns are ignored.
Conclusion
CMS calculations begin with gross annual income supplied by HMRC and convert that figure into a gross weekly income for statutory assessment purposes. In most cases, historic tax-year earnings form the basis of the calculation, even where current circumstances differ significantly.
While the system aims to provide consistency and administrative efficiency, reliance on historic income can sometimes produce outcomes that appear disconnected from a parent's current financial reality. The 25% variation rules, current income reviews, shared care reductions and protected earnings provisions are intended to address these issues, although concerns about affordability and responsiveness remain among many parents using the scheme.
Understanding how CMS moves from annual earnings to weekly income is essential when checking whether a maintenance calculation is accurate, fair and reflective of actual circumstances.
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