民國八十八年六月二十二日立法院三讀通過營業稅法第十一條修正條文，將銀行、保險等七大行業的營業稅率由5％降為2％，此次營業稅調降對於政府營業稅稅收影響重大（政府每年的稅收損失約420億元，占當年營業稅收16.9％），並引發後續之稅率調降風波（三大工商團體要求金融業之營業稅稅率降至為零）。本研究的主旨是探討該降稅事件對於金融業營收管理之影響，首先以T統計量檢定八十八年度第二季之營業收入是否存在非預期之波動，其次，以迴歸分析解釋該季之非預期波動的可能原因。實證結果顯示； 1.民國八十八年第二季營業收入的實際變動顯著低於預期應有之正常波動，而上述營業收入的非預期波動於民國八十八年第三季及第四季並不會重複發生，支持本文之推論，即因營業稅率調降之營收管理現象僅存在於八十八年度第二季。 2.民國八十八年第二季營業收入的非預期波動與自有資金比例有負向關係，而與買賣票券利益（淨額）有正向關係。此外，公營銀行民國八十八年第二季營業收入的非預期波動大於非公營銀行。 過去一般研究企業之盈餘管理，較著墨於盈餘與股價之實證關係，而對於金融業之研究範疇也多侷限於資本適足率等議題，本文藉由此次營業稅稅率之調降，針對該稅率調降前之八十八年度第二季進行實證研究，金融業者是否利用稅率變動期間進行營業收入之管理，及其解釋因素之探討，研究結果有下列參考之價值（1）提供財政部賦稅署估計稅率變動所產生之潛在稅收損失，（2）提供投資人與債權人關於金融業季報表之可靠性評估，（3）提供稅率改變之租稅動機對於盈餘管理相關議題的實證研究。 / June, twenty-second, 1999, the legislative Yuan passed the law reform of Operating Tax, and lowered the operating tax rate of banks, insurance, and other financial organizations from 5 percent to 2 percent which had great influence on the government’s revenue of operating tax and gave rise to the following incident of tax rate lowering. This study’s main object is to investigate whether operating revenues of financial organizations are managed in response to the change in the operating tax rate. First, testing if there exists any unexpected fluctuation in the second quarter’s operating revenue by T-test. Second, using regression model to explain the possible causes of that quarter’s unexpected fluctuation. The result of empirical tests show that： 1. The actual fluctuation of 1999 second quarter’s operating revenue is obviously lower then the expected normal fluctuation while the mentioned unexpected fluctuation is not repeated in the 1999 third and fourth quarter, which provides evidence of the phenomenon of deferring operating revenues in response to a large decrease in the operating tax rate only exists in the second quarter of 1999. 2. The unexpected fluctuation of the second quarter’s operating revenue is negatively related with the percentage of self-held capital and positively related with the net gain of securities transactions. Besides, government-held banks’ unexpected fluctuation of the 1999 second quarter’s operating revenue is greater than that of private banks.This study takes interest in the change in the operating tax and investigates whether the tax rate change provides the financiers a substantial incentive to defer their quarterly operating revenue. It also tries to identify situations in which incentives to manage operating revenue exist. The result of this possesses the following contributions：（1）it provides government to measure the potential loss of operating tax revenue when estimating the impact of tax rate changes, and（2）it also provides the investors and creditors to measure the reliability of the quarterly financial statements. Finally,（3）it provides the tax motivation of empirical study to enlarge the related subjects of earning management.