There is no separate "overtime tax". Overtime is added to your gross pay and taxed at your marginal rate — the rate that applies to the last euro you earned.
The standard rate cut-off point
Income up to your standard rate cut-off point is taxed at 20%. Everything above it is taxed at 40%. Add PRSI and USC on top, and the last hours of a heavy overtime week can be reduced by roughly half before they reach you.
A worked example
Say your overtime adds €300 gross in a week, and €120 of it sits above your cut-off point. The €180 below is taxed at 20%, the €120 above at 40% — plus PRSI and USC on the whole €300. The result is a take-home figure well below the headline 1.5× rate you were promised.
It isn't lost money
Because Irish PAYE is cumulative, if your later weeks are quieter your unused band is restored and the tax evens out over the year. You only permanently pay 40% on income that stays above the cut-off point across the full tax year.
See it on your own payslips
MySalaryPal's overtime insight shows exactly what your last block of overtime hours was worth after tax — using your own hourly rate and band position, not a generic calculator.