Section 18National Internal Revenue Code of 1997 (Republic Act No. 8424), Sec. 18

Reports of violation of Laws. - When an internal revenue officer discovers evidence of a violation of this Code or of any law, rule or regulations administered by the Bureau of Internal Revenue of such character as to warrant the institution of criminal proceedings, he shall immediately report the facts to the Commissioner through his immediate superior, giving the name and address of the offender and the names of the witnesses if possible: Provided, That in urgent cases, the Revenue Regional director or Revenue District Officer, as the case may be, may send the report to the corresponding prosecuting officer in the latter case, a copy of his report shall be sent to the Commissioner.