Common CMS Problems: Current Rules & Practical Fixes
These additions use current GOV.UK and DWP guidance and sit above the full original guide.
Income Wrong? Check the 25% Rule
CMS normally starts with the latest available complete-tax-year gross income supplied to HMRC. If a Paying Parent provides evidence of current gross income, CMS says it will normally use the new figure only where it is at least 25% higher or lower than the HMRC figure and the change is expected to be long-term.
Official income rulesPension Contributions: Avoid Double Counting
CMS says taxable gross income is used before Income Tax and National Insurance but after qualifying pension contributions. Employer/occupational pension deductions are usually already reflected in taxable income. Separate private pension contributions may need to be reported.
Pension calculation guidanceSelf-Employment: HMRC Data Is the Starting Point
CMS includes profits from self-employment as income and normally uses information supplied to HMRC through the tax system. Where current income is materially different, provide a clear current taxable gross income figure supported by recent self-assessment or accountant evidence.
Self-employed income guidanceHidden or Diverted Income: Use the Variation Route
Either parent can ask CMS for a variation where additional income or assets should be considered. Current rules include rental income or investment income over £2,500 a year, qualifying assets worth at least £31,250, certain earned income while on the flat rate, and diversion of income.
CMS says it can use sources such as Companies House and must consider whether a variation is just and equitable.
Apply for a variation Receiving Parent variation guideCurrent Shared-Care Bands
For reduced and basic-rate cases, CMS currently reduces maintenance where there are at least 52 agreed overnight stays a year. The published bands are 52–103 nights, 104–155, 156–174, and 175 or more. At 175+ nights, the reduction is 50% plus £7 a week for that child.
If both parents agree shared care exists but cannot agree the exact number above 52, CMS says it can assume 52 nights.
Official shared-care rulesDirect Pay Disputes: Keep Bank Evidence
CMS advises Direct Pay users to keep a record of payments. If a payment is said to be missing, bank statements, standing-order records, transfer references and payment confirmations can be critical.
CMS payment guidanceWrong Decision? Mandatory Reconsideration Is Time-Limited
GOV.UK says a challenge to a CMS payment decision is made through Mandatory Reconsideration, normally within 30 days of the date on the decision letter. If still dissatisfied, a tribunal appeal can normally be made within one month of receiving the MR decision.
CMS complaints & appeals SSCS2 tribunal formComplaint and Appeal Are Different
Use a complaint for poor service, delay, lost correspondence or administrative handling. Use MR/appeal where you are challenging the legal maintenance decision itself. In some cases both routes may be appropriate.
DWP complaints procedureGet the CMS Records Behind the Problem
DWP's Subject Access Request guidance specifically allows you to request your CMS account information and evidence used in a dispute or investigation.
DWP Subject Access RequestIncorrect Data vs Incorrect Decision
If factual personal information is inaccurate, UK GDPR rectification rights may help. But correcting data is separate from overturning a CMS maintenance decision, which normally requires the statutory MR/appeal route.
ICO rectification rightsCMS Problem-Solving Pack
Use one structured pack so the same evidence can support the correct route.
Important: “Hidden Income” Should Be Evidence-Led
A Receiving Parent is entitled to raise a genuine concern about additional or diverted income, but an allegation is not proof. CMS's variation process allows both parents to provide information before a decision is made. Likewise, a Paying Parent should have a fair opportunity to respond with tax, company, payroll or accounting evidence.
Historical Arrears Need Reconstruction, Not Assumptions
Older arrears can involve multiple decisions, effective dates, Direct Pay periods, legacy CSA records and payment-allocation issues. Ask for a period-by-period breakdown and compare it against bank records and CMS/DWP records rather than treating the headline balance as self-proving.
Official CMS Problem-Solving Sources
Common CMS Problems
The detailed guide below preserves all of the content supplied for this page.
Common Child Maintenance Service (CMS) Problems
Income Errors
Ignored Evidence
Delays, Arrears Disputes
Self-Employment
Hidden Income
Shared Care & Your Rights
Many Child Maintenance Service (CMS) cases are managed without major problems. However, parents sometimes encounter difficulties that can affect maintenance calculations, arrears, enforcement action, and overall confidence in the system.
This guide explains some of the most common issues reported by both Paying Parents and Receiving Parents, along with practical steps that may help resolve concerns.
For Paying Parents in particular, maintaining evidence and understanding review, appeal, and complaint processes can be essential where concerns arise regarding false arrears, incorrect calculations, or evidence allegedly being ignored.
CMS Got My Income Wrong
One of the most common concerns raised by Paying Parents is that CMS has used incorrect income information.
Why Does This Happen?
Possible reasons may include:
- HMRC records being out of date.
- Recent employment changes.
- Changes in self-employment income.
- Incorrect tax year information being used.
- Pension contributions not being reflected correctly.
- Employer information not yet updated.
- Administrative errors.
Evidence That May Help
Useful evidence may include:
- Payslips
- P60s
- Tax returns
- Employer letters
- Payroll records
- Pension contribution records
- Accountant evidence
What Should You Do?
Request An Explanation
Ask CMS:
What income figure was used?
What tax year was used?
What evidence was relied upon?
Provide Evidence
Submit relevant documents as early as possible.
Request A Mandatory Reconsideration
If you believe the decision is wrong.
Appeal Where Appropriate
If the dispute remains unresolved.
CMS Ignored Evidence
Another common complaint is that evidence has been submitted but appears not to have been considered.
How Evidence Should Be Considered
Good administrative practice requires decisions to be:
- Evidence-based
- Fair
- Transparent
- Capable of explanation
Relevant evidence should normally be reviewed and considered before decisions are made.
What If Evidence Appears Ignored?
Ask For Clarification
Request:
What evidence was reviewed?
What evidence was rejected?
Why was it rejected?
Resubmit Important Evidence
Provide copies again if necessary.
Create An Evidence Index
List:
- Every document submitted
- Date submitted
- Purpose of the evidence
Escalate If Necessary
Options may include:
- Mandatory Reconsideration
- Tribunal appeal
- Formal complaint
- Independent Case Examiner (ICE)
CMS Delays & Poor Communication
Parents sometimes experience delays or difficulties obtaining information.
Examples Include
- Long response times
- Delayed reviews
- Delayed reconsiderations
- Missing correspondence
- Unreturned calls
- Unclear explanations
Expected Service Standards
Parents should expect:
- Reasonable communication
- Clear explanations
- Timely responses
- Professional conduct
- Accurate record keeping
What Can You Do?
Keep Records
Maintain a timeline of:
- Calls
- Emails
- Letters
- Complaint submissions
Submit A Complaint
Where service standards appear unacceptable.
Escalate Complaints
Through:
- CMS Complaints Team
- Independent Case Examiner (ICE)
- Parliamentary & Health Service Ombudsman (via MP)
CMS Arrears Disputes
Arrears disputes are among the most common and serious concerns raised by Paying Parents.
How Arrears Occur
Arrears may arise due to:
- Missed payments
- Partial payments
- Direct Pay disputes
- Shared care disputes
- Income assessment changes
Administrative errors
- Unrecorded payments
- Incorrect account adjustments
What Should You Do?
Request A Full Arrears Breakdown
Ask for:
- Payment history
- Account statements
- Arrears calculations
- Payment allocation records
Compare Records
Check against:
- Bank statements
- Payroll records
- Direct Pay evidence
Challenge Inaccuracies
Use review and appeal processes where appropriate.
Historical Arrears
Older cases can be particularly difficult due to missing records and historic decisions.
Common Issues
Examples include:
- Lost documents
- Historic Direct Pay disputes
- Missing payment records
- Older maintenance calculations
- Legacy Child Support Agency (CSA) records
Protecting Yourself
Where possible:
Retain historical records.
Request account histories.
Obtain Subject Access Request (DSAR) records.
Compare CMS records against your own evidence.
Self-Employed Parent Income Issues
Self-employment can create additional complexity.
Challenges
Examples may include:
- Fluctuating income
- Business expenses
- Delayed tax information
- Multiple income streams
- Dividend arrangements
Evidence That May Help
- Tax returns
- Business accounts
- Accountant reports
- HMRC records
Variations
In some cases, variation applications may be relevant where income information does not reflect the true financial position.
Hidden Income & Diversion Of Income
Sometimes concerns are raised that income available to a parent is not fully reflected in the standard CMS calculation.
What Does Hidden Income Mean?
Examples may include:
- Undeclared earnings
- Income paid through a company
- Dividend arrangements
- Income diversion
- Income received through third parties
Raising Concerns
Parents should provide evidence wherever possible.
Useful evidence may include:
- Company records
- Public financial records
- Property information
- Financial documentation
CMS should investigate concerns fairly and objectively.
Evidence Matters
Allegations should be supported by evidence wherever possible.
Decisions should not be based on assumptions alone.
CMS & Shared Care Disputes
Shared care is another common area of disagreement.
Why Shared Care Matters
Shared care arrangements can affect child maintenance calculations.
The number of overnight stays may influence maintenance liability.
Common Disputes
Examples include:
- Number of overnight stays.
- Changes to arrangements.
- Informal parenting agreements.
- Court order interpretation.
Evidence That May Help
- Child Arrangements Orders
- Parenting plans
- School records
- Medical records
- Parenting app records
- Communication records
What If CMS Gets Shared Care Wrong?
Parents may wish to:
Submit supporting evidence.
Request a Mandatory Reconsideration.
Appeal where appropriate.
Advanced Claimant Protection
Parents have important rights throughout the process.
Right To Fair Treatment
CMS should act fairly and reasonably.
Right To Evidence-Based Decisions
Relevant evidence should be considered.
Right To Transparency
Parents should understand how decisions were reached.
Right To Accurate Records
Incorrect information should be corrected.
Right To Challenge Decisions
Review, appeal, and complaint routes should remain available.
Right To Accountability
Public authorities remain accountable for errors.
Useful Evidence Checklist
Keep copies of:
- Bank statements
- Payment confirmations
- Payslips
- Payroll records
- Pension contribution records
- Tax returns
- Shared care evidence
- Court orders
- CMS correspondence
- Complaint records
- Tribunal decisions
- DSAR responses
Relevant Legislation
Key legislation includes:
- Child Support Act 1991
- Child Maintenance and Other Payments Act 2008
- Child Support Maintenance Calculation Regulations
- Human Rights Act 1998
- Data Protection Act 2018
- UK GDPR
These legal frameworks support fairness, transparency, accountability, and evidence-based decision making.
Useful Resources
Child Maintenance Service
Open official / referenced resource ↗
Child Maintenance Calculator
Open official / referenced resource ↗
Mandatory Reconsiderations & Appeals
Open official / referenced resource ↗
Appeal A Child Maintenance Decision
Open official / referenced resource ↗
Independent Case Examiner
Open official / referenced resource ↗
Information Commissioner's Office
Open official / referenced resource ↗
Key Message
Most child maintenance disputes can be resolved more effectively when parents maintain organised records, preserve evidence, and understand their rights. Whether concerns involve incorrect income figures, ignored evidence, delays, disputed arrears, self-employment, hidden income, or shared care arrangements, decisions should be based on reliable evidence, accurate records, and fair procedures.
For Paying Parents especially, maintaining independent records of payments, income, shared care arrangements, and communications can provide valuable protection against false arrears, incorrect calculations, and disputes where evidence appears to have been overlooked.
Right First Time UK
Fair Decisions. Public Money. Real Accountability.