What the model does today¶
maintenance_incomeholds child maintenance received. Datasets fill it from the Family Resources Survey child maintenance module.spousal_maintenance_incomeholds maintenance paid by a spouse, civil partner, former spouse or former civil partner (#2572).Both are added to
market_income,household_market_incomeandhbai_household_net_income.maintenance_expenses(maintenance paid) is subtracted inmarket_incomeandhbai_household_net_income.Only
spousal_maintenance_incomefeeds the means tests:Universal Credit unearned income (UC Regulations 2013 reg. 66(1)(d));
Pension Credit income (State Pension Credit Regulations 2002 reg. 15(5)(d)), but not savings credit qualifying income (reg. 9(f));
Housing Benefit income, less £15 a week where the family includes a child or young person (HB Regulations 2006 Sch. 5 para. 47; HB (SPC) Regulations 2006 reg. 29(1)(o) and Sch. 5 para. 20).
UC earned income does not net off maintenance paid.
uc_deductionsdoes cover child maintenance collected from a paying parent’s UC award, but only in aggregate: it sits in the above-cap excess ofuc_deduction_ratewith last resort deductions, estimated from DWP deduction data rather than frommaintenance_expenses.
For child maintenance that is the right answer for UC:
Receiving parent: child maintenance is not unearned income under UC Regulations 2013 reg. 66(1), so it is fully disregarded.
Paying parent: maintenance paid is not deducted, so the paying parent is means-tested on their full earnings.
The paying-parent side of this asymmetry is the work-incentive problem
described by the Centre for Social Justice in The Hidden Parent Poverty Trap:
Child Maintenance and Universal Credit. The model reproduces UC’s side
of it, because neither child maintenance variable reaches UC. It does not
reproduce the combined marginal rates, because maintenance_expenses is a
fixed input that does not rise with earnings.
Scope¶
Phases 1 and 2: separate the inputs and count spousal maintenance¶
Done in the engine by #2572. What remains is in the data: datasets that put
the FRS payments from an absent partner in private_transfer_income should
move them to spousal_maintenance_income
(policyengine
Phase 3: model the CMS calculation¶
Derive the CMS weekly amount when the inputs are available, from the paying parent’s gross weekly income (GOV.UK; Child Support Act 1991 Sch. 1):
| Paying parent’s gross weekly income | Rate | Weekly amount |
|---|---|---|
| Below £7 | Nil | £0 |
| £7 to £100, or on benefits | Flat | £7 |
| £100.01 to £199.99 | Reduced | Formula |
| £200 to £3,000 | Basic | 12% / 16% / 19% of income up to £800 for 1 / 2 / 3+ children, then 9% / 12% / 15% of income from £800 to £3,000 |
| Above £3,000 | Basic, capped | Income above £3,000 is ignored; the receiving parent can apply to the courts |
| Not enough information | Default | £39 / £51 / £64 (SI 2012/2677 reg. 49; GOV.UK’s guide shows £38 for one child) |
Then:
Shared care: for the basic and reduced rates, the amount payable to each carer falls by 1/7 where a child spends 52 to 103 nights a year with the paying parent, 2/7 for 104 to 155, 3/7 for 156 to 174 and 1/2 for 175 or more; where one carer looks after more than one qualifying child, the fractions for those children are added and divided by the number of them (para. 7(5)). It then falls by a further £7 a week for each child with 175 or more nights, but not below £7 a week in total (Sch. 1 para. 7). Where the flat rate applies because the paying parent or their partner gets a prescribed benefit (para. 4(1)(b) or (c) or 4(2)), 52 or more nights with a child makes the amount payable to that child’s carer nil (para. 8).
Other children: an adjustment applies for other children living with the paying parent.
The income bands are fixed in legislation, not uprated each year.
Phase 3 is optional for UC analysis, which needs only Phases 1 and 2. It allows reforms to the CMS rates or bands to be scored.
Implementation outline¶
Parameters under gov/cms/¶
income_bands/: the £7, £100, £200, £800 and £3,000 limits.rate/flat.yaml,rate/default/andrate/basic/(12/16/19% and 9/12/15%).rate/reduced/: the reduced-rate formula.shared_care/: the night bands and fractions.
Variables under variables/gov/cms/¶
child_maintenance_gross_weekly_income(Person)child_maintenance_obligation_pre_shared_care(Person)child_maintenance_shared_care_reduction(Person)child_maintenance_paid_cms_basis(Person, derived award)
Data needs¶
FRS records maintenance received and paid at person level. Phase 1 needs a check of how far its source items separate child maintenance from spousal maintenance.
DWP Child Maintenance Service statistics (quarterly, latest data to June 2026) give the CMS caseload and amounts. They support checking the new inputs, bearing in mind that many families use private (“family-based”) arrangements outside the CMS.