One of the biggest myths in child support is that 50/50 care means no one pays. It doesn't. The formula is income-driven first, care-driven second. Even with exactly equal care, the higher-earning parent typically still transfers money to the lower-earning parent — the gap just narrows. The actual rule: each parent gets a "cost percentage" based on how much care they provide, and that's offset against their share of the combined child support income. The bigger the income gap (or the smaller the care gap), the bigger the payment.
This guide walks through the care bands, the cost percentages they translate into, and how the formula combines them with each parent's income to land on a final number. Every figure here matches the Services Australia formula our Child Support Estimator uses, verified against the Child Support Guide §2.2.1.
The 5 care bands
Services Australia uses 5 care-percentage bands. Each maps to a "cost percentage" — the share of the children's cost that parent is treated as already meeting through their care.
| Care band | Care % | Cost percentage |
|---|---|---|
| Below regular care | 0–13% | 0% (this parent is "paying parent"; no care offset) |
| Regular care | 14–34% | 24% |
| Shared care (lower) | 35–47% | 25% + (care% − 35) × 2% (so 25% at 35%, 49% at 47%) |
| Equal care | 48–52% | 50% (a single band — small variations around exactly half) |
| Shared care (upper) | 53–65% | 51% + (care% − 53) × 2% (so 51% at 53%, 75% at 65%) |
| Primary care | 66–86% | 76% |
| Above primary | 87–100% | 100% (this parent receives; other parent's formula is moot) |
Why the jumps? The bands aren't perfectly linear because the formula was designed to recognise that real care patterns don't usually land at exactly half — small variations (48–52%) are smoothed into equal care, and below 35% care doesn't trigger the same cost-sharing recognition as a meaningful shared arrangement.
How the formula actually combines care + income
The 8 steps Services Australia runs (per Child Support Guide §2.4):
- Child Support Income for each parent = ATI − Self-Support Amount (SSA, $31,046 for 2026).
- Combined Child Support Income = sum of both parents' CSI.
- Each parent's INCOME percentage = their CSI ÷ combined CSI.
- Each parent's CARE percentage → COST percentage via the bands above.
- Each parent's COST share = max(0, income% − cost%). (If your income% is higher than your cost%, you're "under-paying for your share of the kids" and you transfer the difference.)
- Multiply the cost share by the Cost of Children table figure for combined CSI + number of children.
- Round and check against the Minimum Annual Rate (MAR, $519/case for 2026) + Fixed Annual Rate (FAR, $1,720/child up to 3 kids, $5,160 max).
- Final transfer payment = the parent whose cost share > 0 pays the other parent.
Try the free CS calculator → · Open the full estimator → Pop in both incomes + care % + number of kids and we'll show every step of the formula with the actual figures.
Worked example — 50/50 care, unequal incomes
Two parents, one child aged 8, exactly 50/50 care.
- Parent A: ATI $120,000 → CSI = $120,000 − $31,046 = $88,954
- Parent B: ATI $60,000 → CSI = $60,000 − $31,046 = $28,954
- Combined CSI: $117,908
- Income %: A = 75.4%, B = 24.6%
- Cost % (50/50 care): both = 50%
- Cost share: A = max(0, 75.4 − 50) = 25.4%; B = max(0, 24.6 − 50) = 0%
- Cost of Children (table lookup for $117,908 combined, 1 child aged 0–12, 2026): ~$25,000
- Parent A pays: 25.4% × $25,000 = ~$6,350/year (~$528/month) to Parent B.
So with exactly 50/50 care, Parent A still transfers ~$6.3k/year because they earn 2× as much. If incomes were equal ($90k each, equal care), the transfer would settle at $0 — but unequal incomes always produce a transfer regardless of care split.
Worked example — 70/30 care, unequal incomes
Same parents (A: $120k, B: $60k), but now A has 30% care, B has 70%.
- Cost % (30% care for A): regular care → 24%
- Cost % (70% care for B): primary care → 76%
- Cost share: A = max(0, 75.4 − 24) = 51.4%; B = max(0, 24.6 − 76) = 0%
- Parent A pays: 51.4% × $25,000 = ~$12,850/year (~$1,071/month) to Parent B.
Same incomes, different care split → A's payment doubles because B is doing more of the actual day-to-day care and A is doing less of it.
The 87–100% "above primary" trap
If one parent has 87% or more care, the formula treats the other parent as having effectively no care — their cost % is 0%, and the primary carer's cost % is 100%. The high-care parent receives a payment regardless of income difference. For the under-13% care parent, this means even if you're paying for school, sports, or paying for the child to fly to your place a few times a year, the formula doesn't recognise it — you're still classed as below-regular-care.
If your actual care contribution doesn't match the strict night-count Services Australia uses, you can apply for a Change of Assessment to recognise other costs. See our Change of Assessment guide for the grounds and the process.
Why care % matters for FTB-A too
FTB-A applies the SAME care percentages — it's apportioned by your shared-care percentage so each parent receives the right share. With 50/50 care, each parent gets 50% of the FTB-A the family unit would have got. Below 35% care you generally don't qualify for FTB for that child. The CS care % and the FTB care % use the same underlying numbers but are administered separately by two different parts of Services Australia, so they sometimes drift out of sync — worth checking both when care changes.