Red team extended childcare subsidy logic/parameters

[nwoodruff-co]

@PolicyEngine I get 4k for extended childcare subsidy for a 99k-earnings single parent of 2, but think it should be about 9k (8 pounds times 38 weeks times 30 hours per week) in 2025. Can you check the model?

[policyengine]

I've analyzed the extended childcare subsidy calculation. The £4k result is likely correct based on the policy rules, but I need to understand what the expected £9k should represent.

Key findings about the 2025 extended childcare entitlement:

1. Age eligibility matters: Only children aged 9 months+ qualify in 2025

   • Age 0 to <9 months: 0 hours/week
   • Age 9 months to <3 years: 15 hours/week
   • Age 3-4 years: 30 hours/week
   • Age 5+: 0 hours/week

2. Funding rates (from 2024-04-01, with uprating applied):

   • Age 0-1: £11.22/hour
   • Age 2: £8.28/hour
   • Age 3+: £5.88/hour
   • All funded for 38 weeks/year

3. Example calculations for 2025:

   • 2-year-old: 15 hrs/wk × £8.28/hr × 38 wks = £4,719
   • 3-year-old: 30 hrs/wk × £5.88/hr × 38 wks = £6,702
   • Both together: £11,421

The £4k you're seeing suggests only ONE child is qualifying. This could happen if:

• One child is under 9 months old (gets 0 hours)
• One child is age 2 and gets 15 hours/week: 15 × ~£8/hr × 38 = ~£4,560

Can you share the ages of the 2 children in your scenario? That will help me determine if this is working correctly or if there's a bug in the model.

[nwoodruff-co]

@PolicyEngine it's this:

base_situation = {
        "households": {
          "household": {
              "members": ["adult", "child_1"],
          }
      },
      "benunits": {
          "benunit": {
              "members": ["adult", "child_1"],
          },
      },
      "people": {
          "adult": {
              "age": 40,
              "employment_income": emp_income,
          },
          "child_1": {
              "age": 2,
          },
      },
  }

  baseline = Simulation(situation=base_situation)

[policyengine]

Great catch! You're absolutely right - the model had an incorrect date for the childcare expansion.

The Bug:
The parameter file had the 30-hour expansion for 2-year-olds starting on 2026-01-01, but the actual policy change was September 1, 2025.

Why you were seeing £4k instead of £9k:

• With the wrong date: 2-year-old gets 15 hrs/week × £8.49/hr × 38 weeks = £4,839 ❌
• With the correct date: 2-year-old gets 30 hrs/week × £8.49/hr × 38 weeks = £9,678 ✅

The Fix:
I've updated the parameter file to reflect the correct September 2025 implementation date and adjusted all related test cases. The UK government's final phase of childcare expansion doubled free childcare from 15 to 30 hours per week for children aged 9 months to 2 years starting September 1, 2025.

Pull Request: #1456

References:

• UK Government: How to apply for 30 hours free childcare (September 2025)
• Gov.uk: Check eligible free childcare