An internal revenue agent who make arrests and seizures for violation of internal revenue laws or regulations assume the category of peace officers and are, therefore entitled to the privileges of such officers under the Revised Penal Code and Rules of Court. (U.S. vs. Viado, 39 Phil 10)

Revenue agents have no authority to search, without a warrant, a business establishment for supposedly fraudulent records. But they are empowered to seize  said records, discovered in the course of their investigation, pursuant to Sec. 15. (People vs. Rubio, 57 Phil 886)

Pursuant to SEc. 15, only the commissioner, etc. are authorized to arrest and apprehend suspected tax evaders and therefore, the BIR is without authority to authorize any person to help in in apprehending susoected tax evaders. (BIR Ruling No. 10, Jam 1, 1992)