Weekly vs Fortnightly Tax Tables: Why They Differ (2025-26)

General information only. This is not tax or financial advice. PAYG withholding amounts are set by the ATO’s published tax tables and coefficients; confirm the current tables before configuring payroll.

If you are paid weekly and your colleague is paid fortnightly on the same salary, you will not see exactly double the tax on their payslip. That is not a payroll error — it is built into how the ATO constructs its PAYG withholding tables. Here is what is actually going on, and the once-a-decade quirk that can leave fortnightly-paid employees with a tax bill.

What the tables are doing

PAYG withholding is the employer’s best estimate of the annual tax on your salary, sliced into the pay cycle. The ATO publishes separate weekly, fortnightly, monthly and quarterly tax tables, each derived from the same underlying annual rate scale plus a set of withholding coefficients.

The mechanics differ by cycle:

• The weekly table is the base table. Earnings are looked up per week and a withholding amount is read off, rounded to the nearest dollar.
• The fortnightly table is built by halving the fortnightly earnings, applying the weekly coefficients, then doubling the result and rounding.
• The monthly table adds a further rounding rule (cents ending in 33 are first bumped to the next dollar) before the weekly logic is applied to a derived weekly-equivalent amount.

Because each step rounds at a different point, doubling the weekly figure rarely lands exactly on the fortnightly figure. The gap is usually a dollar or two per pay — immaterial over a year, and it washes out at assessment time when your actual annual tax is calculated.

Why the small differences don’t matter (usually)

Withholding is a prepayment, not the final tax. Whatever the weekly-vs-fortnightly rounding does to any single payslip, your end-of-year assessment recalculates tax on your real annual taxable income. Over-withholding becomes a refund; under-withholding becomes a payable. The rounding noise between cycles nets out.

What can matter is a structural mismatch between how many pay periods the tables assume and how many you actually receive.

The 27-fortnight (and 53-week) catch

The ATO’s fortnightly table is calibrated on the assumption that there are 26 fortnights in a year. Most years there are. But because 26 × 14 = 364 days — one short of a calendar year — the extra day (two in a leap year) drifts, and roughly once every 11 years a payroll calendar lands 27 fortnightly pays in a single financial year. Weekly-paid employees hit the same issue as a 53-week year.

When that happens, 27 fortnights of withholding (each calibrated for a 26-fortnight year) under-collects against your now-higher annual gross. The shortfall isn’t an error in any single pay — it’s that you received an extra pay the table never assumed. The result is a smaller refund or an unexpected tax bill at assessment.

The ATO publishes additional withholding amounts for exactly this case: employees who know they’ll be paid 27 times can ask their employer to withhold a set extra amount each fortnight (scaled by income band) so the year still balances. See 27 fortnights in a year: the extra-pay tax catch for the full breakdown and the additional-withholding figures.

Worked example

Sam earns $1,800 a fortnight. The fortnightly PAYG table withholds, say, $330. A weekly-paid colleague on the same annual salary ($900 a week) might have $164 withheld weekly — which is $328 across the fortnight, $2 less than Sam’s fortnightly figure. Neither is wrong; the rounding diverged. Across a standard 26-fortnight year both arrive at the same annual withholding within a few dollars, and assessment reconciles the rest.

But in a 27-pay year, Sam receives an extra $1,800 gross with only standard-table withholding against it — enough to turn a modest refund into a small payable unless the additional-withholding amount was applied.

How to check yourself

Look up the exact table figure for your pay with the fortnightly tax table, or browse the broader 2025 tax tables for other cycles. To see whether your year’s withholding will land you in refund or payable territory, run your full-year salary through the income tax calculator and compare it to total PAYG withheld. For a quick payslip sanity check, see Reading your fortnightly payslip.