Salary Sacrifice, Super & the HECS and Medicare Trap

Salary sacrificing into superannuation (or packaging a car on a novated lease) is one of the most popular ways for Australian employees to reduce their income tax. By directing pre-tax dollars into super up to the annual concessional contributions cap, those dollars are generally taxed at 15% inside the super fund instead of your marginal tax rate plus Medicare levy.

However, thousands of Australians get an unexpected bill at tax time because they assume reducing their Taxable Income also reduces their HELP/HECS repayment or keeps them below the Medicare Levy Surcharge (MLS) threshold. It does not.

Here is how the math actually works, and how to model it before you change your payroll settings.

How Pre-Tax Super Salary Sacrifice Reduces Income Tax

When your employer pays your salary, they must pay the compulsory Superannuation Guarantee (SG) on top of your ordinary time earnings. Both your employer's SG contributions and any voluntary pre-tax salary sacrifice (or personal deductible super contributions) count toward your annual concessional contributions cap.

Example: $110,000 Base Salary

Suppose you earn $110,000 and decide to salary sacrifice $10,000 into super over the financial year:

1. Your Taxable Income drops from $110,000 to $100,000.
2. Instead of paying your marginal income tax rate plus the 2% Medicare levy on that $10,000, your super fund deducts 15% contributions tax ($1,500), putting $8,500 net into your retirement balance.
3. Your immediate annual tax saving is the difference between your marginal tax rate (plus Medicare levy) and the 15% super tax rate.

You can test the exact impact on your weekly, fortnightly, or monthly take-home pay in our Australian Salary Calculator, and project how that extra $8,500/year compounds over 20 years in the Super Calculator & Estimator.

The Repayment Income Trap: Why Salary Sacrifice Does Not Lower HECS/HELP

If you have a HELP, HECS, VSL, or STSL student loan, the ATO does not calculate your compulsory repayment using your Taxable Income. Instead, it uses Repayment Income (RI):

Repayment Income = Taxable Income + Reportable Super Contributions + Reportable Fringe Benefits + Total Net Investment Loss + Exempt Foreign Employment Income

What does this mean in practice?

• When you salary sacrifice $10,000 into super, your Taxable Income drops by $10,000—but your employer reports that $10,000 as a Reportable Employer Superannuation Contribution (RESC) on your income statement.
• The ATO adds that $10,000 right back in when calculating your HELP repayment!
• Even worse: if your payroll software only withholds PAYG tax based on your reduced $100,000 cash salary, too little HELP repayment may be withheld during the year, leaving you with a tax bill when you lodge your return.

1. Gross base salary$110,000
2. Pre-tax super salary sacrifice-$10,000
3. Reduced Taxable Income (used for income tax)$100,000
4. Reportable super contribution (RESC) added back+$10,000
5. HELP & MLS Repayment Income (unchanged!)$110,000

Feature	Reduces Taxable Income	Reduces HELP Repayment Income	Reduces MLS Income
Work-related deductions (D1–D5)	Yes	Yes	Yes
DGR charity donations (D15)	Yes	Yes	Yes
Tax agent & accounting fees (D10)	Yes	Yes	Yes
Pre-tax super salary sacrifice (RESC)	Yes	No	No
Personal deductible super contributions	Yes	No	No
Reportable fringe benefits / packaging	Yes	No	No
Negative gearing (net investment loss)	Yes	No	No

The Medicare Levy Surcharge (MLS) and Reportable Fringe Benefits

The same "add-back" rule applies to the Medicare Levy Surcharge (MLS): the extra 1% to 1.5% surcharge levied on higher earners who do not hold an appropriate level of private patient hospital cover for the full financial year.

Income for MLS purposes adds back:

• Reportable super contributions (salary sacrifice and personal deductible super)
• Reportable fringe benefits (such as charity/NFP salary packaging or a taxable novated lease)
• Net investment losses

As a result, you cannot use super salary sacrifice to drop below the Medicare Levy Surcharge threshold. In fact, if you package a benefit that creates a grossed-up Reportable Fringe Benefit Amount (RFBA)—including certain FBT-exempt electric vehicle novated leases, which are still reportable on your income statement!—your Income for MLS Purposes and Repayment Income can actually increase.

Checklist Before Setting Up Salary Sacrifice

1. Check your remaining concessional super cap: Ensure your employer SG plus your proposed salary sacrifice will not exceed the annual concessional cap (unless you are eligible to use carry-forward unused concessional cap amounts from the prior 5 years and your Total Super Balance was under $500,000 at 30 June).
2. Model your net pay and HELP repayment: Enter your salary, student loan toggle, and voluntary super amount in the Australian Salary Calculator, and check the compulsory repayment under the new marginal schedule in the HECS-HELP Calculator (explained in our 2025–26 repayment changes guide).
3. Project your long-term retirement balance: See what an extra $100 or $200 a fortnight does to your future balance in the Super Calculator.
4. Track your work-related tax deductions: Unlike salary sacrifice, legitimate work-related deductions (D1–D15) reduce both your Taxable Income and your Repayment Income. Keep your receipts organized all year with PFinance's Tax Deduction Tracker.

For how concessional contributions fit alongside investing outside super, our investment basics guide covers the super-vs-brokerage trade-off.