Check "REGISTERED ACTIVITY(IES)" in your Certificate of Registration.
If you see a line saying "WITHHOLDING TAX - EXPANDED/OTH" then YES, you are required to withhold taxes whenever you pay any of your suppliers.
As a withholding agent, you also have to file two more additional tax forms:
Form 0619E
Monthly Remittance Form of Creditable Income Taxes Withheld
Submitted every February, March, May, June, August, September, November, and December
Each filing covers the previous month
Form 1601EQ
Quarterly Remittance Return of Creditable Income Taxes Withheld
Submitted every April, July, October, and January
Each filing covers the previous quarter
To find out how withholding taxes are entered in Taxumo, go here:
How to do I enter withheld taxes if I am the withholding agent?