Were you able to meet the "Officer of the Day", John Paul? Under Item #19 of BIR Form 1901 I wrote my full name as my business name and "freelance contractor" as my occupation. Taxes that are applicable to me are income tax (quarterly and annual), other percentage taxes under the National Internal Revenue Code (specifically Monthly Percentage Tax), and registration fees. PSIC codes will be filled up by BIR.
I am not familiar with the "Professional Tax Receipt" that Francisco suggests. I checked "sole proprietorship" as my taxpayer type.
This is how my O.R. looks like:
I wonder how it will be if you choose "professional" as your taxpayer type. That would be interesting, don't you think? Now, I feel excited as to the outcome of your "study".