Below is a sample computation of withholding tax on compensation.
Assuming Total Taxable salary of Php 40,000
(Basic Php30,000 +Allow Php10,000)
Deduct SSS, Philhealth and Pag-ibig
SSS Php581.30
Philhealth Php412.50
Pag-ibig Php100.00
Net Taxable Income is Php38,906.20 (Php40,000-581.30-412.50-100)
To get the tax rate, check the MONTHLY Compensation level (CL) where the taxable income falls, for no. 1 its the tax rate for Php20,833 below, for no.2 its Php20,833 and above but should be less than Php33,333 (why it should be less than Php33,333 because no.3 is for income Php33,333 and above)
For the sample computation, the Taxable income of Php38,906.20 falls on no.3 because its more than Php33,333 but less than Php66,667.
So the tax is Php2,500 plus 25% of (Taxable Php38,906.20-Php33,333 CL)
So Php2,500 + 25% of Php5,573.20
So its Php2,500 + Php1,393.30
Total tax due Php3,893.30
_________________________________________________________
The computation for semi monthly is actually the same as monthly, the difference is, the Philhealth, SSS and Pag-ibig contributions will depend on the deduction of your employer which some they deduct it at one time on end of month or divide it by two for deduction on first half and end of the month.
For computation purposes lets assume the deduction is in half and details are below:
Basic salary Php15,000
Other Php5,000
Deduct below contributions:
SSS Php290.65
Philhealth Php206.25
Pagibig Php50
Net Taxable Income is Php19,453.10
To get the withholding tax due, check the tax table again for SEMI MONTHLY Compensation Level. With the amount above it will fall on no. 3 because Php19,453.10 is greater than Php16,667 but less than the amount on No.4 which is Php33,333.
Tax is Php1,250 + 25% over CL (which is Php19,453.10 less Php16,667)
Php1,250 + 25% of Php2,786.10
Php1,250 + 696.525
So, your semi monthly withholding tax is Php1,946.525
