Taiwan Tax Agreement Act of 2023 This bill authorizes the United States to enter into a tax agreement with Taiwan. Specifically, the President may, through the American Institute in Taiwan (AIT), negotiate and enter into a tax agreement with the Taipei Economic and Cultural Representative Office (TECRO). (The U.S.-Taiwan relationship is unofficial; TECRO is Taiwan's principal representative office in the United States, while the AIT, a private corporation, performs many of the same functions as U.S. embassies elsewhere.) The agreement must address issues including (1) the taxation of tax residents of Taiwan, the United States, or both; (2) relief from double taxation; and (3) protection against tax evasion or avoidance. The agreement must conform with the 2016 U.S. Model Income Tax Convention and other customary U.S. bilateral income tax convention terms. The bill requires the President to notify Congress 15 days before negotiations begin and provide periodic briefings. The Department of the Treasury must brief Congress upon request and provide timely updates during the course of negotiations. The negotiated agreement may only take legal effect upon submission of the agreement to Congress and the approval of a concurrent resolution in a form prescribed by the bill. The agreement, once in force, must be afforded the same treatment as a treaty under U.S. law.