Backpay Calculator Australia — Underpayment Calculator

What Is Back Pay?

Back pay is money your employer owes you for work you have already done but were paid too little for. It covers wages below your award or agreement rate, missed penalty rates, overtime, allowances and leave loading, and the super that should have been paid on them. It also describes a pay rise that is backdated to an earlier start date.

How Is Backpay Calculated in Australia?

Backpay is the difference between what you should have been paid and what you were actually paid, multiplied by the total hours worked during the underpayment period. The Fair Work Ombudsman uses a straightforward formula:

(Correct hourly rate - Actual hourly rate) x Total hours worked = Wage shortfall

In addition to the wage shortfall, your employer also owes:

• Unpaid superannuation: The 12% SG applies to the underpaid amount. If you were paid $26.44/hr instead of $30.00/hr, your employer owes an additional $0.43/hr in super on the $3.56 difference.
• Unpaid leave accrual: Annual leave accrues on ordinary hours. Underpayment means your leave balance was also underpaid when you took or cashed out leave.
• Interest: In some cases, the Fair Work Ombudsman or courts may award interest on unpaid wages, particularly for prolonged underpayments.

Check the correct rate for your role using the Award Rates page, which lists minimum pay rates by industry classification, or run your award, level and hours through the Fair Work pay calculator.

How Is Backpay Taxed?

Backpay received as a lump sum is taxed under the ATO's Schedule 5 tax table for back payments, commissions, bonuses, and similar payments. Your employer withholds tax at a rate that considers your regular earnings plus the lump sum.

Back pay is assessed in the year you receive it, not the years it relates to. If part of it accrued more than 12 months before payment (reported as lump sum E) and that part is 10% or more of your income for the year, the ATO may apply a lump sum payment in arrears tax offset so the spike does not cost you more than if you had been paid on time. You don't apply separately: include the year-by-year breakdown when you lodge and the ATO works it out.

Use the Income Tax Calculator to see how the lump sum affects your tax bracket, or the Bonus Tax Guide for details on lump sum taxation.

How to Make an Underpayment Claim

If you believe you have been underpaid, follow these 4 steps:

1. Check your correct rate. Find your award or enterprise agreement on the Fair Work website. Use the Award Rates page to look up your classification and minimum rate.
2. Gather evidence. Collect payslips, time sheets, rosters, bank statements, and your employment contract. Compare the hours worked against the pay received.
3. Raise it with your employer. Many underpayments are genuine errors. Write to your employer (keep a copy) requesting they review your pay and rectify the shortfall.
4. Lodge a complaint. If your employer does not resolve the issue, lodge a complaint with the Fair Work Ombudsman online at fairwork.gov.au or call 13 13 94.

Under the Fair Work Act, you generally have 6 years from when an underpayment happened to recover it. Since 1 January 2025, intentional underpayment can also be a federal criminal offence.

Common Types of Underpayment

The Fair Work Ombudsman identifies 5 common underpayment types in Australian workplaces:

• Below-award base rates: Paying less than the minimum hourly rate for the employee's classification level.
• Missing penalty rates: Not paying weekend, public holiday, or overtime loadings as required by the award. Cafes, pubs and restaurants are the most common source of these claims; check the Hospitality Award Pay Rates 2026-27 if that is your industry.
• Unpaid overtime: Requiring employees to work before or after shifts without recording or paying the hours.
• Incorrect casual loading: Paying casual employees without the required 25% casual loading on top of the base rate.
• Super shortfall: Not paying the 12% superannuation guarantee on all ordinary time earnings. Use the Superannuation Calculator to verify your employer's contributions.

Frequently Asked Questions

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