The FHSS benefit is driven by: (1) the tax saving on the way in, and (2) the deemed earnings rate on the way out.
On the way in — lower contribution tax:
When you salary sacrifice $15,000 into super, it is taxed at 15% rather than at your marginal rate. For someone earning $90,000 (marginal rate 32% including Medicare), salary sacrificing $15,000 saves approximately $2,850 in income tax that year compared to saving the equivalent after-tax amount.
2025-26 Australian tax brackets (excluding Medicare levy):
| Taxable Income | Marginal Rate |
|---|
| $0 – $18,200 | 0% |
| $18,201 – $45,000 | 16% |
| $45,001 – $135,000 | 30% |
| $135,001 – $190,000 | 37% |
| $190,001+ | 45% |
Plus 2% Medicare levy for most residents.
On the way out — 30% tax offset:
Concessional contributions and deemed earnings are included in your assessable income for that year, but a 30% tax offset applies. For someone on $90,000 (32% marginal + Medicare), effective withdrawal tax on the assessable portion is about 2%. Non-concessional contributions are not taxed at withdrawal.
Deemed earnings:
The ATO applies deemed earnings at the shortfall interest charge (SIC) rate — 90-day bank bill rate plus 3%, updated quarterly. Current rate 6.61% p.a. (Oct–Dec 2025). This is a notional figure regardless of what your super fund actually earned.
Important limitations:
- HECS/HELP: Salary sacrifice is counted as reportable employer super contributions (RESC), which can increase your HELP repayment income. Check with your accountant or payroll before setting up salary sacrifice.
- Division 293: If income plus concessional contributions exceeds $250,000, you pay an extra 15% tax on those contributions — this significantly reduces the FHSS benefit for very high earners.
- Deemed vs actual returns: The ATO uses the SIC rate at withdrawal regardless of your fund's actual performance.