Child maintenance income change checker
Written by James Whitfield · Last reviewed 29 October 2026
If the paying parent's income goes up or down by 25% or more, or stops, GOV.UK says either parent must report it to the Child Maintenance Service. Smaller changes are usually picked up at the annual review, which uses HMRC's latest income figure.
This is a change of 25% or more. GOV.UK says either parent must report it to the Child Maintenance Service.
Estimates use the CMS rules with no shared care or other children. The CMS decides whether and when to change the amount.
How income changes are handled
Each case is reviewed every 12 months, on the anniversary of when the paying parent was told about the application. The review uses the latest income HMRC holds.
When the CMS checks current income, it uses the HMRC figure unless the paying parent's current income differs from it by 25% or more, in which case it uses the newer figure.
The 25% figure is a test the CMS applies. It does not mean the amount changes automatically, and the CMS decides when any new amount starts.
Other changes to report
GOV.UK also lists a change of main carer, a change to how often the child stays overnight, moving house (within 7 days), adding a child to the case, and a child leaving the UK. Report online through your account, or contact the Child Maintenance Service.
Questions
Do I have to report a pay rise to the CMS?
GOV.UK says either parent must report if the paying parent's income changes by 25% or more, or stops. Smaller changes are picked up at the annual review.
What if my income falls?
A fall of 25% or more should be reported. The CMS may then use your current income instead of the HMRC figure.
Sources
- GOV.UK: Child Maintenance Service, report a change (checked 29 October 2026)
- GOV.UK: Child maintenance annual review: how it works (updated 8 April 2024) (checked 29 October 2026)
- GOV.UK: How child maintenance is worked out (checked 29 October 2026)
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