Resumo
When both parents work, the second salary doesn’t all come home. Income tax, National Insurance, childcare fees, commuting costs, and work expenses eat into it — sometimes dramatically. This calculator compares three scenarios: both parents working, Person A quitting, or Person B quitting. It shows which option leaves the household with the most disposable income.
Como funciona
The calculator models three scenarios and compares the household disposable income in each:
- Both work — combined take-home pay minus childcare, both commutes, and both sets of work expenses
- Person A quits — only Person B’s take-home pay, but no childcare costs (parent at home), no commute or expenses for Person A
- Person B quits — only Person A’s take-home pay, same logic in reverse
For each scenario, household disposable income is calculated as:
Where
The second job gain shows how much each person’s job really adds to the household:
Where
If the second job gain is negative, the household is financially better off with that person not working.
Childcare costs in the UK
Average UK childcare costs vary significantly by type, age of child, and region.
Full-time nursery costs (2025)
| Region | Under-2 (50 hrs/week) | 3-4 year olds |
|---|---|---|
| England average | Lower (free hours apply) | |
| Inner London | Higher | |
| North East | Lower |
Source: Coram Family & Childcare Survey 2025.
What you lose if one parent quits
Two major government schemes require both parents to be working:
- 30 free childcare hours (worth £6,000–£8,000/year at nursery rates) — both parents must earn at least £195/week and neither can earn over £100,000
- Tax-Free Childcare (up to £2,000/child/year) — same dual-working requirement
If one parent quits, the family drops from 30 free hours to just the universal 15 hours (for 3-4 year olds only), and loses the Tax-Free Childcare top-up entirely. These hidden costs are not modelled in the calculator’s numbers but are flagged in the disclaimer.
Exemplo prático
Person A earns £50,000, Person B earns £35,000, 1 child
Person A take-home pay (after tax and NI)
= £39,520
Person B take-home pay
= £28,720
Both work: combined net minus all costs
= £47,840/yr (£3,987/mo)
Person B quits: A's net minus A's costs only
= £35,320/yr (£2,943/mo)
Second job gain from B's £35k salary
= £12,520/yr (£1,043/mo)
Result
Person B's £35,000 job adds just £12,520/yr (£1,043/mo) to the household after childcare, commuting, and expenses. Both working is still worthwhile.
When quitting makes sense
With 2 children at £15,000 childcare each, Person B earning £25,000, and £4,000 in commute/expenses, Person B’s job actually costs the household £12,480/year. The calculator correctly recommends Person B quitting.
Entradas explicadas
- Person A / B gross salary — annual salary before any deductions
- Number of children — determines total childcare cost (cost per child × number)
- Childcare cost per child — annual cost per child for nursery, childminder, or after-school care. Use the pre-subsidy cost (before free hours or Tax-Free Childcare)
- Commute cost — annual cost of getting to work (rail, fuel, parking, etc.)
- Work expenses — annual costs you wouldn’t have if you stayed home: bought lunches, professional clothing, parking, subscriptions
Resultados explicados
- Household disposable income — what’s left after tax, NI, childcare, commuting, and work expenses for each scenario
- Best option — which scenario (both work, A quits, or B quits) leaves the most disposable income
- Second job gain — how much each person’s job really adds to the household after all associated costs
- Break-even childcare cost — the childcare cost per child at which quitting becomes financially better than both working
Premissas e limitações
- Tax calculation uses 2025/26 UK rates — income tax bands and NI thresholds for England, Wales, and Northern Ireland (not Scotland)
- No pension modelling — salary sacrifice pension contributions reduce taxable income but also reduce take-home pay. The calculator assumes no pension deductions.
- No student loan modelling — student loan repayments further reduce take-home pay but are not included
- Childcare is modelled as a flat annual cost — the calculator does not model free hours, Tax-Free Childcare, or childcare vouchers. Users should input their actual out-of-pocket cost.
- No Child Benefit or HICBC — these are not included in the calculation. Child Benefit adds £1,355-£2,252/year depending on number of children, but HICBC claws it back for earners above £60,000.
- No Marriage Allowance — if one parent quits, they could transfer £1,260 of unused personal allowance to their partner (saving £252/year). This is not modelled.
- Career break costs are not quantified — lost pension contributions, reduced future earnings, and gaps in employment history are flagged but not calculated
- Non-financial factors are not modelled — wellbeing, child development, career satisfaction, and personal preference are important but outside the scope of a financial calculator
Verificação
| Test case | Inputs | Expected disposable | Our result | Source |
|---|---|---|---|---|
| Both work, mid-income | A=£50k, B=£35k, 1 child £13k, commute £3k/£2k, exp £1.2k/£1.2k | £47,840/yr | £47,839/yr | Manual calc against gov.uk tax rates |
| B quitting makes sense | A=£80k, B=£25k, 2 children £15k each, commute £4k/£3k, exp £1.5k/£1k | B quits: £51,457/yr | £51,457/yr | Manual calc |
| Equal earners | A=£40k, B=£40k, 1 child £8k, commute £2k/£2k, exp £1k/£1k | Symmetric: A quits = B quits = £29,320/yr | £29,320/yr | Manual calc |
Sources
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