Taxpayer of estate tax or gift tax who, in violation of Article 23 or 24 herein, fails to file the tax return as required before the prescribed deadline, or in violation of Article 26 herein, fails to apply for extension to file return, the competent tax authority should initiate investigation immediately, complete the investigation and determination of tax due within the time limit stipulated in Article 29 herein, and notify the taxpayer to pay tax pursuant to Article 30 herein.