Enforcement Rules of the Income Tax Act Article 50
The date of filing shall be based on the date the tax return is delivered to the tax office; the tax return sent by mail shall be done by registered mail, and the date stamped and shown on the mail shall be the filing date; for a tax return sent through the Internet, the date the filed information is transmitted to the tax office shall be the date of filing.
中文原文 所得稅法施行細則第50條
申報日期，應以申報書送達稽徵機關之日為準；其郵遞者，應以掛號寄送，並以交郵當日郵戳日期為申報日期；透過網際網路傳輸者，應以申報資料傳輸至稽徵機關之日為申報日期。