If your take-home pay dropped late in the year, it is almost always tax annualisation — not a change to your tax rate.
Each payday, tax is withheld as an estimate. Starting around October, Outstaffer payroll totals your actual full-year income and computes the exact tax due under the Bureau of Internal Revenue (BIR) graduated tables (TRAIN law), then trues up what you have already paid.
If too little was withheld earlier, the shortfall is collected across your remaining payslips — so your deduction goes up. If too much was withheld, the excess is refunded (no later than 25 January).
It usually rises because a raise, bonuses, or a mid-year start left earlier months under-withheld. Your total tax for the year is unchanged — annualisation only corrects the timing of what was withheld.