本研究探討關聯企業聘用相同會計師或事務所查核，對關聯企業租稅規避的影響。會計師對於企業的整體營運及內部運作有相當程度的瞭解，若其同時查核關聯企業，有助於企業稅務資訊的確認與品質提升，甚至可以依據關聯企業的整體營運活動，提供一致的最適租稅規劃建議。本研究以臺灣上市櫃企業在2000 年至2016 年共9,821 個觀察值為樣本，檢視企業與其關聯企業所聘用會計師或事務所的名單，辨認企業與關聯企業聘用相同會計師或事務所的情況，分別採用相同會計師或事務所的虛擬變數、總數及比例，作為企業與其關聯企業聘僱相同會計師或事務所查核的程度之衡量。實證結果發現，企業與其關聯企業僱用之會計師若相同，企業的租稅規避程度愈高，且僱用相同會計師或事務所家數或比例愈高，企業租稅規避程度愈高。此外，以人工方式蒐集企業關係人交易類型資訊，發現當企業關係人交易類型為進貨或應付款項，其交易金額最大的關聯企業聘用相同會計師或事務所查核時，企業租稅規避程度也愈高。

This research examines the data of same accounting firms and same accountants between affiliated companies from 2000 to 2016 to study the relationship between same accountants and tax avoidance. Due to the understanding of companies’overall operations while auditing them, accountants are able to confirm and improve the quality of tax information. Therefore, same accounting firms (same accountants) may provide the most optimal tax planning recommendation to affiliated companies according to their operations. This research first examines the list of accounting firms and accountants employed by companies, then measure the extent to which the company and its affiliates hire the same accountants by three different mathods. Research shows that tax avoidance is higher when companies hire same accounting firms (same accountants) with their affiliated companies. In addition, the research collects different types of related party transactions manually, and finds that affiliates who hire same accountants, with the largest related party transaction amount, have higher tax avoidance.

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