It is normal for take-home pay to change between weeks, especially for hourly or roster-based workers. Changes often come from hours worked, overtime, allowances, and PAYG withholding adjustments.
Overtime and penalty rates: Extra hours or higher weekend/holiday rates increase gross income, which increases PAYG withholding for that pay period.
Progressive tax withholding: Employers estimate your annualised income using ATO formulas. Higher earnings in a single week may temporarily increase withheld tax.
Tax-free threshold changes: If you update your TFN declaration or switch employers, your PAYG withholding may shift when the threshold is added or removed.
HELP/HECS adjustments: When your employer detects you have a HELP/HECS debt, additional withholding is applied. This can cause lower take-home pay.
Other employer deductions: Union fees, salary sacrifice, novated lease payments, and other pre-tax or post-tax deductions change your net income.
How this calculator models weekly changes: This site shows consistent calculations based on your hourly rate or weekly input. It does not model employer-specific rounding or ATO withholding formulas.
Call to action: Use this calculator to sanity-check weekly and fortnightly payslips and compare them with your expected gross and net pay.