Salary sacrificing means asking your employer to pay part of your pre-tax salary into super instead of your bank account. Inside super it's taxed at 15%; in your pay it's taxed at your marginal rate. The benefit is simply the gap between those two rates.
The maths
On a $95,000 salary (a 30% marginal rate plus 2% Medicare), sacrificing $10,000 saves $3,200 in income tax. The fund takes 15% ($1,500), leaving you about $1,700 ahead — roughly 17c per dollar sacrificed.
When it isn't worth it
If your income is under $18,200 you pay no income tax, so sacrificing would actually cost you 15%. The benefit also shrinks near the tax-free threshold, and high earners over $250,000 face Division 293, which lifts the super tax to 30% — still below the top 47% marginal rate, but less compelling.
Don't blow your cap
Salary sacrifice plus employer SG must stay within the $30,000 concessional cap (2025–26). Going over means the excess is taxed at your marginal rate.