Why Your Payslip May Not Match an Overtime Calculator

General Calculators Use Defaults — Awards Use Specifics

An online overtime calculator uses common default assumptions — a typical overtime threshold, a typical penalty rate, a typical casual loading percentage. These defaults often reflect the most common provisions across many Modern Awards, but they are not tailored to any particular award or enterprise agreement.

Your actual pay depends on the specific provisions of the instrument that covers your employment. If your award differs from the defaults — even slightly — the result will be different. That difference is not necessarily an error on either side.

Below are the most common reasons a payslip figure may differ from a general calculator estimate.

1. Award Classification Level

Most Modern Awards have multiple classification levels (e.g. Level 1, Level 2, Level 3) with different pay rates at each level. A calculator that uses a base rate you enter will produce results based on that rate — but if your payslip uses a rate from a different classification level than you expected, the total will differ.

Your classification should be set out in your employment contract or confirmed by your employer. You can find the pay rates for each classification level in the Fair Work pay guides for your award.

2. Enterprise Agreement Instead of Award

If your workplace has a registered enterprise agreement, that agreement — not the underlying Modern Award — sets your pay rates and conditions. Enterprise agreements can have different overtime thresholds, different penalty rates, different casual loading percentages, or different methods for calculating interactions between them.

Enterprise agreements must pass a "better off overall test" compared to the relevant award, but individual provisions within an agreement may be higher or lower than the award equivalents. A general calculator will not know the details of your specific enterprise agreement.

3. Salary Set-Off Clauses

Some employees are paid an annualised salary with a set-off clause — a provision that says the fixed salary is intended to cover certain entitlements (such as overtime and penalty rates), up to a specified number of extra hours per year.

Under a set-off arrangement, your payslip may show the same amount each fortnight regardless of how many overtime hours you worked — because the employer treats the salary as already compensating for those hours. Whether this is legally valid depends on whether the salary genuinely covers all entitlements. Fair Work Ombudsman has guidance on annualised salary arrangements.

4. Allowances

Allowances are additional payments for specific conditions of work — such as a tool allowance, uniform allowance, travel allowance, first-aid allowance, or a shift loading. They are separate from the base rate and overtime entitlements.

A general calculator typically does not include allowances. If your payslip includes allowances your employer is required to pay, the payslip total may be higher than the calculator estimate. Conversely, if a calculator is being used to check whether you are being paid enough, allowances add to the entitlement — not just the base rate.

5. Time Off in Lieu (TOIL)

TOIL (time off in lieu) is an arrangement where overtime hours are compensated with time off instead of a cash payment. Under some awards and agreements, employers and employees may agree in writing to TOIL instead of overtime pay.

If your employer is applying TOIL to some of your overtime hours, those hours will not appear as overtime pay on your payslip — instead they are being accrued as leave time. A general calculator assumes all overtime is paid in cash and cannot account for TOIL arrangements.

6. Roster Rules and Averaged Hours

Some awards allow for averaged hours arrangements, where ordinary hours are averaged over a set period (e.g. a roster cycle of several weeks). Under these arrangements, overtime is calculated on the average over the cycle, not on a week-by-week basis. A week with 42 hours may produce no overtime if it is averaged against a lighter week to give a cycle average of 38 hours.

These arrangements must generally be in writing and agreed to by the employee. They are common in industries with variable rosters — hospitality, retail, and transport among them.

7. Public Holiday Rules and Substitution Days

Not all public holidays are the same under every award. Some awards allow a public holiday to be substituted for another day (e.g. the business agrees to observe a different day in place of the gazetted holiday). If a substitution applies, the entitlements relate to the substituted day rather than the gazetted public holiday.

Additionally, part-time and casual employees may have different public holiday entitlements than full-time employees — some casual employees may not be entitled to payment for a public holiday they do not work. See Public Holiday Pay: What to Check.

8. Payroll Rounding

Some payroll systems round hours or dollar amounts to the nearest cent, nearest minute, or nearest quarter-hour. These rounding conventions can produce small differences between a calculator result and the payslip total, particularly across multiple pay periods.

Rounding is generally acceptable in Australian payroll provided it does not systematically disadvantage the employee. If rounding consistently produces a lower result than the employee is entitled to, it may be an underpayment issue worth raising with the employer or Fair Work.

Checklist: What to Ask Your Employer or Payroll Team

If you have raised the matter with your employer and remain concerned, contact the Fair Work Ombudsman for guidance.

See also: How to Check an Overtime Calculation • Calculation Methodology • Australian Pay Terms Glossary