UK Child Maintenance Calculator
On a £500/week gross income with 2 children and no shared care, the statutory Basic rate applies: 16% of gross income = £80.00/week (£346.67/month). Add 60 nights/year of shared care and it drops to £68.57/week. Enter your own income, children and shared-care nights below — the calculator shows every step of the CMS formula, not just the final number.
Based on the statutory CMS formula (2026-07-09). Not legal advice — the official CMS calculation (child-maintenance.dwp.gov.uk) is the binding one.
£80.00 per week
rate band: Basic
Monthly: £346.67 · Annual: £4,160.00 · Per child: £40.00/week
How this figure was worked out — every step
| Step | Value |
|---|---|
| Gross weekly income (Step 1) | £500.00/week |
| Relevant other children adjustment (Step 2) | None — no other children supported, so gross weekly income is unchanged. |
| Rate band (Step 3) | Basic rate — gross weekly income (£500.00) is between £200.00 and £800.00 inclusive. |
| Percentage applied (Step 5, 2 children) | 16% × £500.00 = £80.00/week total (before shared care) |
| Shared care (Step 6) | 0 nights/year — no reduction. |
gov.uk's own calculator returns a single number with no visible working. This breakdown shows the rate band selected, the income adjustments applied, the percentage used, and the shared-care maths — the same steps as the official DWP leaflet's worked examples.
Same income and children — how shared-care nights change the amount
| Nights/year | Band | Total /week | Per child /week |
|---|---|---|---|
| 0 | 0-51 nights/year | £80.00 | £40.00 |
| 52 | 52-103 nights/year | £68.57 | £34.28 |
| 104 | 104-155 nights/year | £57.14 | £28.57 |
| 156 | 156-174 nights/year | £45.71 | £22.86 |
| 175 | 175+ nights/year (half share) | £26.00 | £13.00 |
All five scenarios use the same income, rate band and other-children reduction — only the shared-care nights change. v1 assumes the same nights band applies to every child.
Statutory Child Maintenance Service (CMS) formula, 2026-07-09, verified against gov.uk (DWP leaflet "How we work out child maintenance", updated 1 April 2026) and nidirect.gov.uk. Educational estimate for England, Wales and Scotland cases — it doesn't model collection fees, court-ordered top-ups above the £3,000/week cap, or per-child shared-care schedules that differ between siblings. It is not a substitute for an official CMS calculation or legal advice. How we calculate →
The CMS formula, tranche by tranche
The Child Maintenance Service (CMS) works out how much a paying parent owes using gross weekly income — not net — run through five rate bands. Below £7/week it's the Nil rate (£0). From £7.00 to £100.00 it's the Flat rate: a flat £7.00/week total, regardless of how many children. From £100.01 to £199.99 it's the Reduced rate: £7.00 on the first £100, plus a percentage (17% for 1 child, 25% for 2, 31% for 3+) on the slice above £100.
From £200 to £800, the Basic rate applies: a flat percentage of gross weekly income — 12% for 1 child, 16% for 2, 19% for 3 or more. On our worked example — £500/week, 2 children — that's 16% × £500 = £80.00/week.
Above £800.01, the Basic Plus rate applies: the Basic-rate percentage on the first £800, plus a lower percentage (9%/12%/15% for 1/2/3+ children) on the slice from £800 to £3,000. On £1,200/week with 1 child, that's 12% × £800 + 9% × £400 = £132.00/week. If the parent's income is unknown and they haven't cooperated, CMS uses a Default rate instead: £39/week for 1 child, £51 for 2, £64 for 3 or more.
Two reductions: other children at home, and shared-care nights
If the paying parent supports other children at home (for whom they or their partner get Child Benefit), their income is reduced before the Basic or Basic Plus percentage is applied — by 11% for 1 other child, 14% for 2, 16% for 3 or more. On our £500/week, 2-children example, adding 1 other child at home cuts the income used from £500 to £445.00, and the maintenance owed from £80.00 to £71.20/week.
Shared-care nights — nights the child stays with the paying parent — reduce the amount separately, in four bands: 52-103 nights (1/7 off), 104-155 nights (2/7 off), 156-174 nights (3/7 off), and 175+ nights (half off, plus an extra £7/week per child). The reduction is applied per child: the total is split evenly across children, each child's share is cut by its band, then the shares are added back up — and the CMS rounds only the final total, not each step. Here's what that does to our £500/week, 2-children example at every standard band, side by side:
0 nights/year (0-51 nights/year) → £80.00/week total, £40.00/week per child · 52 nights/year (52-103 nights/year) → £68.57/week total, £34.28/week per child · 104 nights/year (104-155 nights/year) → £57.14/week total, £28.57/week per child · 156 nights/year (156-174 nights/year) → £45.71/week total, £22.86/week per child · 175 nights/year (175+ nights/year (half share)) → £26.00/week total, £13.00/week per child
No source we reviewed — not gov.uk, not nidirect, not the private calculators that rank alongside the official tool — shows shared-care nights compared side by side like this for the same income and children. This v1 assumes the same nights band applies to every child; if siblings have different shared-care schedules, the real CMS calculation can differ from this simplified comparison.
Worked examples, calculated end to end
£500/week, 2 children, no other dependants, no shared care: Basic rate, 16% × £500 = £80.00/week (£346.67/month, £4,160.00/year).
Same income, plus 1 other child supported at home: income is reduced by 11% to £445.00 first, then 16% is applied → £71.20/week.
Same income and children, but 60 shared-care nights/year: the £80.00 total is split to £40 per child, each cut by 1/7 (the 52-103 nights band), then re-summed → £68.57/week — £11.43 less than with no shared care.
£1,200/week, 1 child, no other dependants, no shared care: Basic Plus rate — 12% on the first £800 (£96.00) plus 9% on the remaining £400 (£36.00) → £132.00/week.
The £3,000/week cap and cases the formula doesn't cover
Gross weekly income above £3,000 is ignored by the statutory formula — CMS only calculates maintenance on the first £3,000. If the paying parent earns more, the receiving parent can apply to the courts for a "top-up order" covering income above the cap; that isn't something this calculator (or the statutory formula) estimates.
Parents can also skip CMS entirely with a family-based (private) arrangement — any amount they agree between themselves, with no CMS fees and no fixed formula. This calculator only estimates the statutory amount CMS would set if asked to calculate it.
A government reform was announced in mid-2025 to change how CMS collects payments (moving toward a flat 2% fee structure and phasing out the fee-free "Direct Pay" option). As of the most recent DWP guidance this reform is announced, not yet in force — it would affect collection fees and payment method only, not the income-percentage formula this calculator uses.
Frequently asked questions
Is child maintenance based on gross or net income?
Gross weekly income — before tax, National Insurance or pension deductions (except contributions to a private pension, which are deducted first). This is a common point of confusion: an older, retired pre-2012 scheme used net income, but the current CMS formula does not.
How much is child maintenance for 2 children on £500 a week?
About £80.00 a week (£346.67 a month) under the Basic rate (16% of gross weekly income), assuming no other children supported and no shared care. Adding 60 shared-care nights a year brings it down to about £68.57 a week.
Does 50/50 shared care mean no child maintenance is owed?
If day-to-day care is exactly equal between both parents, the Nil rate applies and no maintenance is owed under the statutory formula. Shared care below that (but at least 52 nights/year) reduces the amount rather than removing it — see the nights-band comparison above.
What is the maximum child maintenance the CMS formula covers?
Gross weekly income above £3,000 isn't included in the formula — CMS calculates on the first £3,000 only. The receiving parent can ask a court for a top-up order above that, which this calculator doesn't estimate.
Does having other children reduce how much I pay?
Yes, if you support other children at home (for whom you or your partner get Child Benefit) and you're on the Basic or Basic Plus rate, your income is reduced by 11-16% (depending on how many) before the maintenance percentage is applied. On the Reduced rate, a different dedicated percentage table applies instead.
Is this the same as the official gov.uk calculator?
No. This is a data-house estimate built from the published statutory formula, designed to show every calculation step. The gov.uk / CMS calculator (child-maintenance.dwp.gov.uk) is the official, binding tool — use it, or contact CMS directly, for anything that needs to be legally accurate.
Researched & verified by the Calcuris Data & Research Team. How we build and check our tools →