本研究探討我國課稅所得之衡量基礎，除理論探討外，亦利用大法官會議解釋第377、722及703號探討制度之選擇與適用。所得之衡量基礎主要有權責發生制與現金收付制，因為權責發生制下，個體提供之報導資訊包含經濟資源與請求權及其變動之資訊，相較於現金收付制僅報導該期間現金收取及支付之資訊，更能提供評估個體過去與未來績效之資訊，應為較佳之選擇。但制度選擇時必須充分考量其成本與效益，故建議立法裁量時，屬利潤性個人所得之會計基礎，以權責發生制為原則，對非利潤性所得(如薪資)或小規模營業者，可例外規定或允許其選擇現金收付制或收付實現制。此外亦建議應修定所得稅法中有關個人所得法中之各人所得衡量基礎之規定以同時符合租稅法律主義；且修定所得法時應重新考慮與調整現行 分類標準，除依所得之本質定性外，亦將稅基之衡量基礎考慮在內，以同時符合課稅平等原則及實質課稅原則。關鍵字:租稅、租稅平等原則、租稅法律主義、實質課稅原則、大法官會議解釋、會計基礎、權責發生制、現金收付制、所得稅法、憲法 This study discusses the measurement basis on taxable income. The research includes the discuss of system selection based on theory and the application of the measurement basis using the issues in J. Y. Interpretation No. 377, 722 and 703. The measurement bases include accrual basis and cash basis. The accrual basis should be a better choice, because the reporting under the accrual accounting would provide the information about entity’s economic resources and claim and the change of them, compared to the cash basis that only reports the cash receipt and payment information. The information based on accrual basis also provides information for the assessment of entity’s performance on the past and future. Of cause, the choice of measurement basis must take full account of the costs and benefits of the system. When the legislative discretion is made, the study recommends that using the accrual basis for the income from business operation, and the income from non-business activities (such as salary payment) or small business operators may be exceptions or allowing it to choose cash basis. In addition, the study suggests to amendment the measurement basis in the income tax law relating to individual income in compliance with the principle of taxation by law. The amendment of income tax law should reconsider the existing classification standards according to the nature of income, and also taking into account the measurement basis of tax base in order to meet the taxation principle of equality and the principle of taxation principle of substance-over-form.