You normally work out how much child maintenance to pay in the UK using the official Child Maintenance Service (CMS) formula, based mainly on your gross weekly income, how many children you’re paying for, and how many nights they stay with you each year.

Key formula in simple terms

For most employed or self‑employed people, CMS looks at your gross weekly income (before tax, but after pension contributions) from HMRC and then applies percentage bands.

Typical basic‑rate percentages (when your gross weekly income is roughly £200–£3,000) are:

  • 1 child: about 12% of gross weekly income.
  • 2 children: about 16% of gross weekly income.
  • 3 or more children: about 19% of gross weekly income.

There are other bands too: very low incomes can be on a nil or flat rate (often £7 per week), and where income is unknown a default amount is used (£38 for 1 child, £51 for 2, £64 for 3+).

How overnights affect the amount

If your child stays overnight with you on a regular basis, the CMS reduces what you pay.

Typical shared‑care reductions per child are:

  • 52–103 nights per year: about 1/7 (14.29%) reduction.
  • 104–155 nights: about 2/7 (28.57%) reduction.
  • 156–174 nights: about 3/7 (42.86%) reduction.
  • 175+ nights: 50% reduction plus an extra £7 off per week.

Even with reductions, payments generally cannot fall below £7 a week where the flat rate applies.

Practical example

Imagine:

  • Your gross weekly income is £600.
  • You pay for 1 child who stays with you 80 nights a year.

A typical calculation would look like:

  • 12% of £600 = £72 per week base amount.
  • 80 nights falls in the 52–103 band, so apply a 1/7 reduction: £72 − £72/7 ≈ £61.71 per week.

This is an illustration using publicly available calculators that mirror CMS rules.

Using the official calculator

To get a figure tailored to you (and something you can show the other parent), you should:

  1. Find your gross weekly income from payslips or HMRC.
  1. Count how many children you pay for in total (including any in your household).
  1. Work out roughly how many nights per year the child(ren) stay with you.
  1. Plug these into the official online child maintenance calculator on GOV.UK, which shows what CMS would likely decide and gives a weekly amount to use in discussions.

Parents are free to agree a different amount privately if it better fits the child’s needs, but the CMS figure is the standard reference used across England, Wales, Scotland and Northern Ireland.

HTML table of the main bands

html

<table>
  <thead>
    <tr>
      <th>Gross weekly income band</th>
      <th>CMS rate type</th>
      <th>Typical weekly amount / rule</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>Below £7</td>
      <td>Nil rate</td>
      <td>£0 per week [web:3]</td>
    </tr>
    <tr>
      <td>£7 to £100, or on certain benefits</td>
      <td>Flat rate</td>
      <td>£7 per week total [web:3]</td>
    </tr>
    <tr>
      <td>£100.01 to £199.99</td>
      <td>Reduced rate</td>
      <td>Formula using a portion of income plus £7 [web:3][web:6]</td>
    </tr>
    <tr>
      <td>£200 to £3,000</td>
      <td>Basic rate</td>
      <td>Approx. 12% (1 child), 16% (2), 19% (3+) of gross weekly income before shared-care reductions [web:3][web:7][web:8]</td>
    </tr>
    <tr>
      <td>Over £3,000</td>
      <td>Top-up via court</td>
      <td>CMS applies formula up to £3,000; receiving parent can ask court for extra [web:3][web:9]</td>
    </tr>
  </tbody>
</table>

Quick reminder

  • The exact figure depends on your real income, benefits, other children you support, and the overnight pattern.
  • For a precise number, always run your details through the official GOV.UK calculator and, if things are complicated or disputed, consider independent legal or mediation advice.

Information gathered from public forums or data available on the internet and portrayed here.