Child Maintenance Calculator
This CMS calculator estimates your child maintenance using the 2025/26 rate bands — nil, flat, reduced, basic and basic plus — and shared care reductions. Enter the paying parent's gross weekly income, the number of children, benefit status and shared care nights, then click Calculate Payment.
Ready to calculate
Enter your details and calculate to see your estimated child maintenance amount using the CMS 2025/26 rates shown below.
Important: This is an independent estimator for planning. It is not a legal determination and does not replace an official CMS decision.
CMS Child Maintenance Rates 2025/26
The Child Maintenance Service decides how much child maintenance you pay from your gross weekly income (earnings before tax and National Insurance but after pension contributions). Your income places you in one of five rate bands. The table below shows the official CMS 2025/26 rate bands and percentages. The calculator above gives a quick planning estimate based on these rates; only a formal CMS calculation is legally binding.
| Rate Band |
Gross Weekly Income |
How Much You Pay |
| Nil rate |
Under £7/week (or full-time student, prisoner, under 16) |
£0/week |
| Flat rate |
£7 to £100/week, or on certain benefits |
£7/week |
| Reduced rate |
£100.01 to £199.99/week |
£7 flat for the first £100, plus a percentage of income over £100 (17% for 1 child, 25% for 2, 31% for 3+) |
| Basic rate |
£200 to £800/week |
12% (1 child), 16% (2 children), 19% (3+ children) of gross weekly income |
| Basic plus rate |
£800.01 to £3,000/week |
Basic rate on the first £800, then 9% (1 child), 12% (2), 15% (3+) on income above £800 |
Only the first £3,000 of gross weekly income is counted. If the paying parent earns more than £3,000 a week, the receiving parent can apply to the court for a top-up order. If the CMS cannot work out the income (for example, no information is supplied), a default rate applies: £39 a week for 1 child, £51 for 2 children, and £64 for 3 or more children. Source figures are taken from GOV.UK (see Official Sources below).
Shared Care Reduction Table
Shared care reduces the maintenance amount when the child regularly stays overnight with the paying parent. The CMS counts the number of nights per year and applies a fraction reduction:
| Shared Care Nights Per Year |
Average Per Week |
Reduction Applied |
| Fewer than 52 nights |
Under 1 night |
No reduction (100% of amount) |
| 52 to 103 nights |
1 night |
1/7 reduction (6/7 of amount) |
| 104 to 155 nights |
2 nights |
2/7 reduction (5/7 of amount) |
| 156 to 174 nights |
3 nights |
3/7 reduction (4/7 of amount) |
| 175+ nights |
4+ nights |
Halved, plus a further £7/week reduction per child |
Key point: shared care is applied after the rate amount is worked out. First find the nil, flat, reduced, basic or basic plus figure, then apply the nights reduction. If care is shared exactly equally and the child lives with the paying parent at least as much as the other parent, no maintenance may be due.
How Is Child Maintenance Calculated?
Most parents start with one question: how much will I actually pay or receive each week? Child maintenance is income-led, sensitive to the number of children, and adjusted for overnight (shared) care. This is why two households with similar salaries can end up with different amounts when care patterns differ or one parent is on benefits. The Child Maintenance Service works it out in six steps.
Step 1 – Work out gross income. The CMS uses the paying parent's gross weekly income, taken from HMRC for the latest tax year (earnings before tax and National Insurance, but after occupational pension contributions). Self-employed income is taken from the latest tax return.
Step 2 – Adjust for other factors. Income is reduced for any other children the paying parent already supports, and for pension payments not already accounted for. Income above the £3,000 weekly cap is ignored.
Step 3 – Find the rate band. Income under £7 a week is the nil rate (£0). From £7 to £100 the flat rate of £7 a week applies. From £100.01 to £199.99 the reduced rate adds a percentage of income over £100 to the £7 flat amount. From £200 to £800 the basic rate applies, and from £800.01 to £3,000 the basic plus rate applies.
Step 4 – Apply the percentage. On the basic rate, the CMS takes 12% of gross weekly income for one child, 16% for two, and 19% for three or more. On the basic plus band, the lower percentages of 9%, 12% and 15% apply to the part of income above £800.
Step 5 – Reduce for other children. The figure is reduced where the paying parent has other dependent children living with them, before shared care is considered.
Step 6 – Apply shared care. Finally, the amount is cut by the shared care fraction: 1/7 for 52–103 nights a year, 2/7 for 104–155, 3/7 for 156–174, and half (plus £7 a week per child) for 175 nights or more. Because care patterns change across a school year, an accurate overnight log is essential — if nights move into a new band, maintenance changes too.
Many disputes happen not because the percentages are unclear, but because parents rely on memory for nights, round income differently, or fail to update arrangements when work changes. To avoid surprises, store weekly income evidence, track overnight stays monthly, and re-run this child maintenance calculator whenever circumstances materially change.
How Much Child Maintenance Should I Pay?
On the CMS basic rate, the amount you pay is straightforward: 12% of your gross weekly income for one child, 16% for two children, or 19% for three or more. For example, a paying parent earning £500 a week pays about £60 for one child (12% of £500), £80 for two (16%), or £95 for three or more (19%) before any shared care reduction. Above £800 a week, the lower basic plus percentages apply to the extra income, so liability rises more slowly at higher earnings.
The reduced rate bridges the gap between the flat £7 and the full percentage. For income between £100.01 and £199.99 a week, the CMS charges £7 for the first £100 plus a percentage of the income above £100 — 17% for one child, 25% for two, and 31% for three or more.
Worked example: a paying parent earns £150 a week with two children. The first £100 attracts the £7 flat amount. The remaining £50 is charged at 25%, which is £12.50. The reduced-rate total is therefore £7 + £12.50 = £19.50 a week before any shared care reduction.
The calculator above gives a quick estimate for budgeting. If both parents can see the same income figures and the same rules, discussions usually become practical rather than emotional, which is often more effective at reducing conflict than arguing over a final number.
Note on planning: if your income is close to a band edge (for example £200 or £800 a week), small changes in overtime, commission or working hours can shift the weekly result. Build a buffer into your budget rather than relying on the exact number shown today.
CMS Vs Family-Based Arrangement: Which Route Fits Better?
Parents generally choose between a private family-based arrangement and the CMS route. A family-based arrangement can be faster to start, often costs less to administer, and can be tailored around school terms, travel costs, and practical realities that a formula may not capture. It can work very well where communication is stable and both parents are consistent. The weakness is enforceability: if payments become irregular, rebuilding trust can be difficult and arrears can grow before either parent acts.
CMS offers structure. It sets out a defined method, keeps records, and provides a route to enforcement when payments break down. For households where communication is low, conflict is high, or financial reliability is uncertain, formal process can reduce uncertainty.
The trade-off is reduced flexibility. Some parents find that a strict formula does not reflect specific household costs, and case administration can feel procedural compared with direct agreement.
In practical terms, the best route depends on reliability and documentation. If both households can agree quickly, maintain records, and adapt calmly when income changes, a family-based arrangement can be effective. If there is repeated non-payment, unresolved disagreement on nights, or frequent income disputes, CMS structure may become necessary. Neither option is automatically better in every case; fit depends on behavior over time.
| Area |
Family-Based Arrangement |
CMS Route |
| Flexibility |
High flexibility on amounts, schedules, and practical extras |
Lower flexibility; formula-led approach |
| Speed to start |
Can start immediately if both agree |
Formal process and administration steps |
| Enforcement |
Limited without legal escalation |
Formal enforcement pathways available |
| Transparency |
Depends on quality of shared records |
Structured calculation and case records |
| Suitability |
Best where trust and communication are strong |
Best where reliability or agreement is weak |
Application Fee, Setup, and Ongoing Reviews
There is a one-off application fee of £20 to open a case with the Child Maintenance Service (some applicants, such as those under 19 or victims of domestic abuse, are exempt). For many households this is the first practical consideration, but it should not be the only one. The larger question is whether the arrangement will stay reliable over time.
A low upfront cost is less valuable if payments then become irregular and require repeated chasing. For that reason, many parents first run a clear estimate, discuss expectations, and document agreed assumptions before selecting a route.
Good setup practice is simple. First, agree what income evidence will be used and how often it will be refreshed. Second, agree how shared care nights will be logged and what counts as an overnight stay.
Third, set review points in advance, for example every six or twelve months, or whenever income changes materially. Fourth, record any additional child-related costs separately from base maintenance so that one-off expenses do not distort the core calculation.
If an agreement starts privately, keep a written summary signed by both parents and date each revision. If discussions break down later, that history can help clarify what was previously accepted. If you proceed through CMS, keep copies of submissions, notices, and payment records in one file. In either route, consistent record-keeping is usually the difference between smooth adjustments and repeated disputes.
When circumstances shift, act early. Waiting months to address changed income or care patterns often creates larger corrections and harder conversations. A practical approach is to run this calculator whenever there is a new work pattern, major overtime shift, or sustained change in care nights. Treat the estimate as a budgeting baseline, then confirm through the formal process when needed.
Worked Child Maintenance Examples (2025/26 Rates)
Example 1 – Flat rate. Gross weekly income is £90, one child, and a few shared care nights. Income between £7 and £100 means the flat rate of £7 a week applies. Shared care below 52 nights gives no reduction. The result is £7 a week, around £30.33 a month and £364 a year.
Example 2 – Reduced rate with shared care. Gross weekly income is £160, two children, and 80 shared care nights a year. The first £100 is charged at the £7 flat amount; the remaining £60 is charged at 25% (two children), which is £15, giving £22 a week. Shared care of 80 nights is the 1/7 band, so the amount is multiplied by 6/7: about £18.86 a week.
Example 3 – Basic rate with two-sevenths reduction. Gross weekly income is £450, one child, and 120 shared care nights. The basic rate for one child is 12% of £450 = £54 a week. Shared care at 120 nights is the 2/7 band, so the final amount is 5/7 of £54, about £38.57 a week. This shows why both income and care data matter — income alone would overstate liability.
Example 4 – Three or more children, half-rate shared care. Gross weekly income is £700, three or more children, and 182 shared care nights. The basic rate for 3+ children is 19% of £700 = £133 a week. Because nights are 175+, the amount is halved to £66.50, then reduced by a further £7 per child for the children in shared care — a substantial cut that shows why accurate annual night totals are critical.
Example 5 – Basic plus rate. Gross weekly income is £1,000, two children, and no shared care. The first £800 is charged at 16% = £128. The remaining £200 (income above £800) is charged at the basic plus rate of 12% = £24. The total is £152 a week. Only the first £3,000 of weekly income would ever be counted.
Example 6 – Nil rate. The paying parent receives qualifying benefits, or earns under £7 a week. The nil rate applies and maintenance is £0 a week. If income or benefit status changes, re-run the calculation so both households can plan around the new figure.
Practical Tips To Avoid Disputes
Use the same definitions each time. Agree what counts as gross weekly income and what documents prove it. Agree what counts as an overnight stay.
Keep one shared record with dates and totals so nobody has to reconstruct a year from memory. Review the amount when there is a clear, sustained change rather than reacting to one unusual week.
When discussions become tense, return to process: same inputs, same formula, same review date. This prevents conversations from turning into personal disputes and keeps focus on child-related stability. If direct agreement is no longer workable, moving to a formal pathway early is usually better than allowing arrears and frustration to build.
Budget conservatively. Maintenance values can change with earnings, hours, and care patterns. A cautious household budget includes a buffer rather than relying on one precise point estimate. That approach protects both households and supports consistent spending for children across the year.
Who Pays Child Maintenance and Who Is Eligible?
Child maintenance is money the paying parent (the parent the child does not mainly live with) gives towards the everyday cost of raising the child. It can be arranged privately as a family-based arrangement, or through the Child Maintenance Service (CMS). The CMS can be used until a child is 16, or 20 if they stay in approved full-time non-advanced education or training.
What counts as gross income
The CMS bases its calculation on the paying parent's gross weekly income — earnings before Income Tax and National Insurance, but after occupational or personal pension contributions. For employees, the figure normally comes from HMRC records for the latest available tax year. For self-employed parents, it is taken from the most recent self-assessment tax return. Income above the £3,000 weekly cap is not counted.
The default rate
If the paying parent does not provide the information needed and HMRC has no figures, the CMS applies a default rate of £39 a week for one child, £51 for two children, and £64 for three or more. This encourages parents to supply accurate income details so a fair amount can be worked out.
Source: GOV.UK — How child maintenance is worked out. Last updated June 2026.
Frequently Asked Questions
1. How is child maintenance calculated?
The Child Maintenance Service works out child maintenance from the paying parent's gross weekly income. That income sets the rate band: nil rate under £7, flat rate of £7 from £7 to £100, a reduced rate from £100.01 to £199.99, the basic rate from £200 to £800, and the basic plus rate from £800.01 up to the £3,000 weekly cap.
On the basic rate the CMS takes 12% of gross weekly income for one child, 16% for two, and 19% for three or more, then reduces the figure for any shared care nights. This calculator follows the same rate bands so you can estimate the result quickly.
2. How much child maintenance should I pay?
On the CMS basic rate you pay 12% of your gross weekly income for one child, 16% for two children, or 19% for three or more. For example, a paying parent earning £500 a week with two children pays roughly £80 a week (16% of £500) before any shared care reduction.
Income above £800 a week uses the lower basic plus percentages (9%, 12% or 15%) on the part above £800, and only the first £3,000 of weekly income is counted. Use the calculator above to see your own figure.
3. Does shared care reduce child maintenance?
Yes. Shared care reduces the amount based on the number of nights a year the child stays with the paying parent: 52 to 103 nights cuts it by 1/7, 104 to 155 nights by 2/7, 156 to 174 nights by 3/7, and 175 or more nights halves it (with a further £7 a week reduction per child).
The reduction is applied after the basic rate has been worked out. Keep a dated overnight record, because evidence quality often decides whether a deduction is accepted without dispute.
4. What are the CMS basic rate percentages in 2025/26?
The basic rate is 12% of gross weekly income for one child, 16% for two children, and 19% for three or more, for income between £200 and £800 a week. Between £800.01 and £3,000 the basic plus rate of 9%, 12% or 15% applies to the part of income above £800. These percentages have not changed for 2025/26.
5. Is this child maintenance calculator an official CMS tool?
No. It is a free independent CMS calculator that applies the published 2025/26 CMS rate bands and shared care rules for planning and budgeting. Official liability can only be confirmed through the formal Child Maintenance Service process and case-specific evidence. There is a one-off £20 fee to apply to the CMS (some applicants are exempt), so check eligibility before applying.
6. Should we use CMS or stay with a family-based arrangement?
If both parents communicate well, keep records, and pay reliably, a family-based arrangement can be efficient and flexible. If communication is difficult or payments are inconsistent, the CMS structure may reduce uncertainty through defined processes and enforceability. The best choice depends less on preference and more on whether your current arrangement performs consistently over time.
7. How often is child maintenance reviewed?
The CMS carries out an annual review and recalculates if income changes by 25% or more. You should also report changes when shared care nights shift into a new band or family circumstances change. Even if life appears stable, an annual check helps avoid sudden corrections and keeps both households informed.
