This child maintenance calculator uses the CMS (Child Maintenance Service) formula to estimate weekly and monthly payments for the 2026/27 tax year. Enter the paying parent's gross annual income, the number of qualifying children and any shared care nights to see the amount due under the basic, reduced or plus rate bands.
CMS basic, reduced & plus rates
The Child Maintenance Service calculates payments from the paying parent's gross weekly income, taken directly from HMRC records. Pension contributions are deducted first. The CMS then applies one of four rate bands depending on the income level, and finally adjusts for shared overnight care.
For most employed parents earning between roughly £10,400 and £183,664 a year, the basic rate applies: 12% for one child, 16% for two, or 19% for three or more. If total gross income exceeds £3,532 per week (about £183,664 a year), a lower plus rate applies to the excess — 9%, 12% or 15% respectively.
Parents on very low income (under £100 per week gross) or on prescribed benefits pay the flat rate of just £8.50 per week, regardless of the number of children. Between £100 and £200 per week a reduced rate tapering formula applies.
| Band | Gross weekly income | 1 child | 2 children | 3+ |
|---|---|---|---|---|
| Nil | Below £7/wk | £0 | ||
| Flat | £7 – £100/wk | £8.50/wk | ||
| Reduced | £100 – £200/wk | Tapering formula | ||
| Basic | £200 – £3,532/wk | 12% | 16% | 19% |
| Plus | Over £3,532/wk | 9% | 12% | 15% |
Source: gov.uk/calculate-child-maintenance. The CMS applies these percentages to gross income after deducting pension contributions.
If the paying parent has the child staying overnight for at least 52 nights a year, the weekly amount is reduced. The more nights of shared care, the larger the reduction:
| Shared nights/year | Reduction |
|---|---|
| 0 – 51 | None |
| 52 – 103 | 1/7 (about 14%) |
| 104 – 155 | 2/7 (about 29%) |
| 156 – 174 | 3/7 (about 43%) |
| 175+ | 1/2 (50%) plus £8.50/child off |
A paying parent earns £35,000 gross per year with no pension deductions and zero shared care nights.
Step 1: Weekly income = £35,000 / 52 = £673.08
Step 2: Falls in the basic rate band (£200 – £3,532/wk).
Step 3: One child at 12% = £673.08 × 0.12 = £80.77/week.
Step 4: No shared care reduction.
Result: £80.77/week = roughly £350/month or £4,200/year.
If the same parent contributed 5% to a workplace pension (£1,750/year), the adjusted weekly income drops to £639.42 and the maintenance falls to about £76.73 per week — saving roughly £210 a year.
CMS uses HMRC data. The actual assessment is based on your most recent tax year's gross income as reported to HMRC, not your current payslip. If your income has changed significantly (up or down by 25% or more), you can request an early review.
The £20 application fee. Applying to the CMS costs £20, waived if you are under 19 or have experienced domestic abuse. Collection charges apply if the CMS has to enforce payments: 20% surcharge on the paying parent's amount and 4% deducted from the receiving parent's payments.
Multiple households. If the paying parent has children in more than one household, the CMS divides the total percentage across all qualifying children before allocating to each receiving parent.
Use the child benefit calculator to see how much Child Benefit you receive — the receiving parent usually claims this. The tax-free childcare calculator shows the government top-up on childcare costs. For overall household budgeting after separation, the take-home pay calculator breaks down your salary after tax and NI.
The Child Maintenance Service uses the paying parent's gross weekly income from HMRC data. It applies a percentage based on the number of qualifying children: 12% for one child, 16% for two children, or 19% for three or more. Pension contributions are deducted first, and shared overnight care reduces the amount.
The basic rate for one qualifying child is 12% of the paying parent's gross weekly income between £200 and £3,532 per week. On income above £3,532 per week the plus rate of 9% applies to the excess. Source: gov.uk/calculate-child-maintenance.
Yes. The CMS deducts pension contributions from gross income before calculating maintenance. This includes workplace auto-enrolment contributions and any additional voluntary contributions into a registered pension scheme.
If the paying parent has the child overnight for at least 52 nights a year, the maintenance is reduced: 52 to 103 nights gives a one-seventh reduction, 104 to 155 nights a two-sevenths reduction, 156 to 174 nights a three-sevenths reduction, and 175 or more nights a one-half reduction.
If the paying parent's gross weekly income is between £7 and £100 or they receive certain prescribed benefits such as Universal Credit without earnings, the flat rate of £8.50 per week applies regardless of the number of children.
No. Child maintenance payments are not taxable income for the receiving parent and are not tax-deductible for the paying parent. They do not appear on a self-assessment return and have no effect on Income Tax or National Insurance.
You do not have to use the CMS. Many separated parents make a private family-based arrangement. The CMS rates still provide a useful benchmark even in a private agreement. If a private arrangement breaks down, either parent can apply to the CMS, which charges a £20 application fee.
The CMS reviews the calculation annually using HMRC data. If income rises or falls by at least 25% between reviews, either parent can request an early reassessment. Changes to the number of shared care nights or qualifying children also trigger a revision.
