HECS Indexation Explained: How Your Student Loan Grows

There is a moment that catches out almost everyone with a study loan. You check your balance in June, after a full year of watching money disappear from every payslip for HECS, and the balance has gone up.

Nothing has gone wrong. It is how the system is built, and it follows from one fact that very few explanations state plainly: the money your employer withholds for HECS does not go onto your loan when it leaves your pay.

Indexation is not interest, but it does compound

A HECS-HELP debt charges no interest. Instead it is indexed on 1 June each year to hold its real value steady as prices rise.

That distinction does not make HELP directly comparable with other forms of borrowing. Two things about it are often understated. Indexation applies only to the portion of your debt that has been unpaid for more than 11 months, so that eligible portion can compound year on year like interest does. Debt you incurred for this year's study is not indexed on the very next 1 June. It has to age first.

How the rate is set

Indexation used to track the Consumer Price Index alone. A 2024 change made it the lower of CPI or the Wage Price Index, and that change was backdated to 1 June 2023 — which is why some people received an indexation credit reversing part of an earlier year.

The rate is worked out after the December CPI and WPI figures are published, using ABS data over the preceding two years.

Recent rates:

The direction matters more than any single year. At 2.8%, indexation on a $30,000 balance is about $840 if the full $30,000 has been unpaid for more than 11 months. Comparing that amount with another form of borrowing would require its own assumptions about rates, fees and repayment terms.

The timing trap, and it is the whole article

Here is the part that produces the June surprise.

PAYG amounts withheld from your pay for HECS are not a repayment. Your employer withholds them and sends them to the ATO, where they sit as tax credits against your account. They are not applied to your loan.

The ATO cannot apply them earlier, and the reason is structural rather than bureaucratic: your compulsory repayment depends on your repayment income for the full year, and nobody knows that figure until the year has ended and you have lodged. Until then, the withholding is only an estimate collected in advance. The loan is reduced when your return is processed and the compulsory repayment is actually raised.

Follow the calendar through and the consequence is stark. Money withheld from your pay across July 2025 to June 2026 is credited to your loan only after you lodge your 2025-26 return, which is July 2026 at the earliest. The indexation on 1 June 2026 is therefore applied to a balance that reflects none of that year's withholding.

So the sequence a lot of people experience is exactly right, even though it feels wrong: a year of repayments comes out of your pay, indexation is applied on 1 June as though it had not, and the repayment lands afterwards.

There is a harder version of the same complaint, and it is not a timing illusion. Your compulsory repayment is a percentage of your income while indexation is a percentage of your indexation-eligible balance, so below a certain income the second is simply larger than the first and the debt grows every year regardless of timing. If the full $30,000 balance is eligible at 2.8%, you need to earn roughly $75,200 before the compulsory repayment even covers the indexation.

Voluntary repayments are applied differently from compulsory repayments.

How voluntary repayments affect the indexed balance

Only the part of the balance sitting on your loan on 1 June that has been unpaid for more than 11 months is indexed. A voluntary repayment is applied to the loan when it is received, rather than waiting for a tax return.

Worked example

Assume you owe $30,000 on 1 June, the full $30,000 has been unpaid for more than 11 months and indexation is 2.8%:

• Indexation added: 2.8% × $30,000 = $840
• New balance: $30,840

If a $5,000 voluntary repayment has been allocated before 1 June and the remaining $25,000 has been unpaid for more than 11 months, indexation applies to $25,000 instead — $700, a difference of $140 for that year.

The repayment system changed, and most guides still describe the old one

This is worth knowing because it changes the arithmetic for anyone near the threshold.

Until 2024-25, compulsory repayments worked on a flat rate applied to your total repayment income. Cross a band boundary by a dollar and the higher rate applied to every dollar you earned, which produced real cliffs.

From 2025-26, the lower formula bands apply marginal rates to income above their thresholds. In the top formula band, the amount is 10% of total repayment income. The final compulsory amount is also limited by the statutory least-of rule: the applicable formula, 10% of repayment income or repayable debt. For 2026-27:

The $9,028.35 base is the 15% amount accumulated up to $129,717 under section 154-20(2) of the Higher Education Support Act 2003. The ATO summary table displays that base as $9,028; this table uses the statutory formula at cents precision. At the top boundary, the 17% formula is $18,604.96, four cents below 10% of total repayment income; the switch to 10% at $186,051 does not create a cliff. Under section 154-20(1), the compulsory repayment is the least of the applicable income formula, 10% of repayment income and the person's repayable debt. Amounts paid reduce repayable debt under section 154-15, so the formula figures in this article assume the repayable debt is at least that amount.

These are formula figures, not a determination of domestic liability for every debtor. Under section 154-1(2), the domestic amount is not payable when the Medicare-levy exception applies. A separate overseas-debtor levy may apply to a foreign resident whose assessed worldwide income exceeds the minimum repayment income; that measure includes repayment income and foreign-sourced income. This article's table does not assess either exception or calculate the overseas-debtor levy.

Two things follow. First, crossing the threshold no longer produces a cliff — at $69,600 the income-based formula is about $11 before the repayable-debt cap, not a percentage of the whole $69,600. Second, the top band remains a rate on total repayment income, not a rate on the excess above a threshold.

The HELP Repayment Threshold page carries the current bands, and the HELP/HECS Calculator projects a balance forward. The Salary Tax Calculator shows what the repayment does to your take-home pay.

Voluntary repayments and compulsory repayments

A voluntary repayment reduces the loan balance. The statutory compulsory repayment remains subject to the least-of rule in section 154-20(1): the applicable income formula, 10% of repayment income or the person's repayable debt. A payment may therefore affect the amount required where it reduces the repayable debt below the income-based amount.

Indexation rates can also change. It was 4.7% when first applied in 2024, before the backdated recalculation brought it to 4.0%. The lower-of-two-indices rule does not fix the rate at a particular level.