1. Contact the tax bureau: You can contact the local tax bureau directly and report the suspected tax evasion to them. The Inland Revenue Department will investigate and handle your report.

2. Provide relevant evidence: When reporting to the tax bureau, try to provide detailed information and relevant evidence for the tax bureau to investigate. This may include the name, address and transaction records of the enterprises or individuals involved.

3. Protect personal information: When reporting, you can ask the tax bureau to protect personal information and report anonymously. This will ensure your safety and avoid potential retaliation.