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Still Their Dad

Does overtime affect child maintenance?

Short answer: yes. The Child Maintenance Service works out your payments from your gross annual income reported to HMRC, and that includes overtime, bonuses and commission. So a year with a lot of overtime can push your maintenance up.

How it works

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The CMS normally takes your gross income from your most recent tax year, straight from HMRC. It does not separate “basic pay” from overtime, it is all just gross income. That figure is set at your annual review and usually holds for the year.

The catch with a high year

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If last year was unusually high (a lot of overtime, or a one-off bonus), your maintenance for the coming year is based on that higher figure, even if your income has since dropped back to normal.

What you can do

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  • Between annual reviews, the CMS will only recalculate if your income has changed by 25% or more (this threshold is under review and has been reported as dropping to 15%, see our update on the CMS changes). If your income has fallen by that much, report it.
  • If the calculation is based on out-of-date income, you can ask for a mandatory reconsideration. Evidence helps: recent payslips, or a letter from your employer confirming the overtime has stopped.
  • The CMS may tell you it needs several payslips before it will act. Put the request in anyway with whatever you have, and keep a copy.

The full breakdown of how the figure is built up is on child maintenance and the CMS.

Where to get real help

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Last reviewed: 18 June 2026. CMS rules and figures change, so check the official links above before you rely on anything here.