Calculation Methodology

Income for MLS Purposes

The Medicare Levy Surcharge is not assessed on taxable income alone. Instead, the ATO uses a broader income measure called income for MLS purposes, which captures economic capacity that taxable income may understate. The calculator computes this as the sum of four components:

Where:

• Taxable Income — assessable income minus allowable deductions, as reported on your tax return
• Reportable Fringe Benefits — the grossed-up taxable value of fringe benefits shown on your payment summary (e.g., novated leases, entertainment)
• Reportable Super Contributions — employer super contributions above the Superannuation Guarantee, including salary sacrifice amounts directed to super
• Net Investment Losses — total net investment losses for the year, including negative gearing losses on rental properties and share portfolio losses

MLS Tier System

The ATO applies a four-tier system to determine your MLS rate. Each tier has separate income thresholds for singles and families. The 2025–26 thresholds were increased for the first time since 2014–15, following a decade-long freeze.

MLS applies to your entire income for MLS purposes once you exceed a threshold — not just the portion above it. There is no graduated phase-in. Crossing the Tier 1 threshold by even $1 triggers MLS on your full income, which is why thresholds are critical decision points.

Couples and families use the family thresholds. If your family status changes during the year (e.g., marriage, separation), MLS is assessed on a daily basis for each applicable period.

Tier Lookup Algorithm

The calculator determines your MLS tier using a backward-iteration algorithm. It starts at the highest tier (Tier 3) and works down, returning the first tier where your MLS income meets or exceeds the minimum threshold.

For families, the algorithm uses adjusted thresholds (see Family Threshold Adjustment) rather than the base thresholds. For singles, the base thresholds are used directly.

• Backward iteration guarantees the highest applicable tier is selected
• Family status (single, couple, family) determines which threshold column is used
• The Tier 0 fallback ensures every input returns a valid result

Family Threshold Adjustment

Families with dependent children receive higher income thresholds, reducing the likelihood of MLS. The adjustment increases the family threshold by $1,500 for each dependent child after the first:

The adjustment only applies when there are more than one dependent child. This shift applies to the Tier 0 ceiling, which effectively pushes all higher tier boundaries upward by the same amount.

For couples without children, the base family thresholds apply with no adjustment. Singles always use the single thresholds regardless of dependents.

Annual MLS Calculation

Once the applicable tier is determined, the annual MLS liability is a simple percentage of your full MLS income:

Key characteristics of this calculation:

• Full-income application: the rate applies to your entire MLS income, not just the portion above the threshold. There is no marginal or progressive calculation
• No phase-in: unlike the Medicare Levy itself which has a shade-in range, MLS has hard thresholds with no gradual ramp-up
• Rounding: the result is rounded to the nearest dollar using Math.round()
• Zero result: if you hold qualifying private hospital cover or your income is below the Tier 1 threshold, the annual MLS is $0

Private Health Insurance Rebate

The Australian Government provides an income-tested rebate on private health insurance premiums. The rebate percentage varies by your MLS tier and age bracket. Higher-income earners receive a smaller rebate, and those in Tier 3 receive no rebate at all.

These rebate percentages are for the period 1 July 2025 to 31 March 2026 and are used across the full financial year in our calculations. Rebate rates are updated annually by the Department of Health and may change from 1 April 2026.

The calculator looks up the rebate using your age bracket and the tier index determined from your MLS income. The rebate is then applied to the gross cover cost to determine the net out-of-pocket premium.

Indicative Cover Costs

The break-even analysis requires an estimate of what qualifying private hospital cover would cost. The calculator uses indicative annual premiums representing basic hospital cover — the minimum level that satisfies the MLS exemption:

The net cost of cover is calculated by applying the applicable PHI rebate to the gross premium:

Break-Even Analysis

The core purpose of the calculator is to answer: “Would I save money by taking out private hospital cover instead of paying the MLS?” The break-even analysis follows a six-step pipeline:

1. 1Calculate MLS income from the four input components (taxable income + fringe benefits + super contributions + investment losses)
2. 2Look up the applicable tier and MLS rate using the tier lookup algorithm, accounting for family status and dependent children
3. 3Calculate annual MLS liability by applying the tier rate to the full MLS income
4. 4Determine PHI rebate percentage based on age bracket and tier index
5. 5Calculate net cover cost by applying the rebate to the indicative gross premium for your family type
6. 6Compare and recommend by calculating the savings and producing a recommendation

The recommendation is determined by the savings figure:

Tier Boundary Display

The calculator UI displays tier boundaries as a visual reference so users can see exactly where their income falls relative to each threshold. Boundaries are computed dynamically based on family status and dependent children:

For Tier 3, the maximum is unbounded (infinity). The boundary display function returns the full set of four tiers with adjusted thresholds, the tier index, and the label and rate — everything needed to render the income bracket visualisation.

This ensures the UI always reflects the correct thresholds for a user's specific family situation rather than showing static base thresholds.

Rounding & Currency Formatting

All MLS calculations use Math.round() for rounding to the nearest whole dollar. This applies to:

• Annual MLS liability
• Net cover cost after rebate
• Savings comparison (MLS minus cover cost)

Currency display uses the JavaScript Intl.NumberFormat API with Australian locale settings:

This produces whole-dollar figures with the $ prefix and locale-appropriate thousand separators (e.g., $1,100, $3,200). Cents are intentionally omitted since MLS is assessed in whole dollars.

Locked Assumptions

The following assumptions are built into the calculation engine. They cannot be changed by the user and are applied consistently across all calculations:

Sources & References

The calculator uses data and methodologies from the following authoritative sources: