If your client withholds your taxes, that does NOT mean you are done. You still have to FILE your own taxes - both percentage and income tax.
As part of filing, that means you compute your own tax dues. The taxes withheld from you will then be deducted from your income tax dues. The resulting net due is your payable income tax to the BIR.
The only exemption would be for people earning less than 250K per year and your client is the only payer/client paying you. In this case though, you have to submit a couple of affidavits attesting to that and you need to provide this to your client.