金融機構之證券交易課稅爭議，往往涉訟金額大，其勝敗對營運活動及 財報數字皆產生重大影響，有時還須訴諸司法院大法官會議作成釋憲解釋。 一旦釋憲解釋公布，纏訟多年的所有稅務爭議，乃至應付稅款所需的現金流 量等同塵埃落定，影響應可觀。根據現金流量假說，當公司未來現金流量改 變時，其市值亦會受到影響。本文透過現金流量假說，利用事件研究法探討 2011 年底司法院公布大法官釋字693 號權證課稅解釋時，相關金融機構之股 價及成交量是否產生異常波動。本研究之實證結果發現，釋字693 號公布 時，因發行權證而未預期現金流出的應補繳稅額愈高者，事件期間之累積異 常報酬率下跌愈多，顯示股市投資人對於大法官解釋之反應，符合現金流量 假說之預期，至於成交量則未有影響。

The outcomes of tax litigation, especially in cases involving controversies over securities trading among financial institutions, usually have a critical impact on the operational activities and financial performance of litigants. The Constitutional Interpretation is the final resort for judicial controversies that might have lasted for years and thus plays a decisive role in the litigation process. From the perspective of cash flow hypothesis, a company’s market value is affected by changes in future cash flows. The empirical results of this study reveal that during the event period when Constitutional Interpretation No. 693 was declared, a considerable decline of cumulative abnormal returns was observed along with high unexpected cash outflows on tax due, this is consistent with the cash flow hypothesis; however, no abnormal trading volume was observed.