以未稽核所得申報資料推估短漏報所得

ESTIMATING UNDERREPORTED INCOME WITH EVIDENCE FROM UNAUDITED TAX RETURNS IN TAIWAN

逃漏稅行為乃所得稅理論與實務研究的重要課題。本文就94年度個人綜合所得稅申報核定檔的抽樣資料，利用納稅人申報之捐贈支出扣除額，以間接推估法推估其隱含的真實所得。實證結果顯示，在綜合所得的各類來源中，以執行業務、利息、租賃及財產交易等四類所得短漏報情形最為嚴重，其申報金額僅為真實所得的三分之一。而營利所得的申報金額與真實所得的差異，主要與資本利得免稅有關，非全因逃漏稅所導致。因此，若能藉完善的會計制度、透明的財務資訊與全面實施發票制度等措施，以增加第三方資訊的提供，將能有效降低所得短漏報程度。

Tax compliance is not only important for the evaluation of tax revenue and social welfare but also critical to the design of optimal taxation. This study utilizes taxpayers’ charitable contributions to infer their actual income and underreported income with the assumptions that taxpayers’ charitable contributions are a function of their income and that the income elasticity of charitable contributions is invariant with sources of income. Based on Taiwan’s unaudited income tax returns in 2005, we find that taxpayers reported only one-third of their income from the second, fourth, fifth and seventh categories to the tax authority, implying a substantial extent of tax evasion for these sources of income. Nevertheless, the gap between the reported income and the actual income from the first category may be mainly attributed to nontaxable capital gains. The findings suggest that more transparent financial information and widespread use of receipts can effectively reduce the extent of income tax evasion.