我國所得稅係採年度申報自繳制度，具有大量、反覆之特性，因此稅捐稽徵機關在所得稅申報期間之前，即已進行各種課稅資訊之蒐集活動，除藉此定出各類所得、費用標準，以作為核課依據外，嗣人民申報其年度所得稅後，即將蒐集之課稅資料與申報資料互相勾稽，作為選定事後審查對象及釐正申報資料與核定所得額之依據；當年度之所得稅申報資料及核定情形復又成為次一年度之課稅基本資料來源及比較對象，二者環環相扣，互為因果關係，形成一個獨立體系，而得以單獨作為研究之對象。次為掌握稅務調查制度之全貌，必須對其作全面性之審視及檢討，故本文採用源自日本之行政法學研究方法「行政過程論」從實現稅務行政目的之過程，歸納、整理所得稅事前課稅資訊蒐集活動及事後審查階段之調查手段、程序、屬性、相關人之法律關係、調查效果及其救濟途徑，以宏觀角度檢視現行法制下之稅務調查制度，藉以發現問題並試圖提出解決方法或修法建議。 / Taiwan adopts an annual self-reporting system for income tax return. Such reporting system involves massive and recurrent information. Hence tax authorities would collect all kinds of tax information before the annual income tax reporting period and use such information to set out the norms for different types of income and expenses as basis for taxation. Upon receiving the annual income tax returns filed by taxpayers, tax officers would check the filed data against the collected tax information, and based on the results, determine the taxpayers to be audited and the assessed income tax. The information contained in an annual income tax return and the results of assessment become the source of basic tax information and comparison for following year’s return. Hence income tax returns of two successive years are interrelated and can form discrete units for research purpose. In order to grasp the full view of the tax investigation system, comprehensive examination of the system is necessary. Thus this study employs the methodology of the “theory of administrative process” originated in Japan to examine the tax investigation system under the prevailing law in a macroscopic manner, from the process of tax administration, pre-filing tax information collection, the means, procedure and attributes of post-filing investigation, legal relationship of the parties concerned, to the effect of investigation and remedies available. This study attempts to discover problems, and based on which, propose solutions or suggestions for regulatory amendment.