The Act Governing Electronic Payment Institutions Article 23

For onshore businesses conducted by specialized electronic payment institutions, the payments between contracted institutions shall be settled and cleared in NTD.For cross-border businesses, businesses specified in Subparagraph 4, Paragraph 1, Article 4 hereof, or related activities approved by the competent authority in accordance with Paragraph 2, Article 15 operated by specialized electronic payment institutions, the payments between onshore users and contracted institutions may be settled and cleared in NTD or foreign currency, whereas offshore payments shall be collected, paid, settled, and cleared in foreign currency.Specialized electronic payment institutions that operate businesses specified in the preceding paragraph and the subparagraphs of Paragraph 1 and Paragraph 2, Article 4 involving exchanges between different currencies shall disclose the exchange rates offered by the bank which they use as reference and the names of cooperating banks on their websites.
中文原文 電子支付機構管理條例第23條
專營電子支付機構辦理我國境內業務,其與特約機構間之支付款項結算及清算,應以新臺幣為之。
專營電子支付機構辦理跨境業務、第四條第一項第四款業務或依第十五條第二項規定經主管機關核准之相關行為,其與境內使用者及特約機構間之支付款項、結算及清算,得以新臺幣或外幣為之;對境外款項收付、結算及清算,應以外幣為之。
專營電子支付機構辦理前項、第四條第一項及第二項各款業務涉及不同幣別間兌換,應於其網頁上揭示兌換匯率所參考之銀行牌告匯率及合作銀行。

English translation for reference only; the Chinese text prevails. Not legal advice.