The CECC stated that in consideration of the status of the COVID-19 pandemic globally, Taiwan would impose 
entry restrictions and quarantine regulations for non-R.O.C. nationals, effective from 00:00 am (local time at the airport of departure) on January 1, 2021, and Taiwan would strengthen quarantine measures form travelers coming to Taiwan, effective from 00:00 am on January 15, 2021.Foreign nationals may enter Taiwan if they hold an Alien Resident Certificate (ARC); for diplomatic or official business; to fulfill contractual obligations; for special humanitarian reasons; when they are the spouse or the underage child of an R.O.C. national; or when they obtain other special permission.Tightened home quarantine measures for travelers entering Taiwan will start from January 15, 2021.Apart from the original requirement of providing a COVID-19 RT-PCR test report issued within three days of boarding, arriving travelers shall also provide proof of the place of quarantine where travelers stay to undergo quarantine (in principle, the place shall be a group quarantine facility or quarantine hotel; those who choose to undergo quarantine at home shall make an affidavit to declare they have met the requirement of one person per residence). Entry quarantine measures will be adjusted on a rolling basis depending on the status of the pandemic and implementation of those measures.
More details on the following websites:
https://www.cdc.gov.tw/En/Bulletin/Detail/6qJb0IbzLMT9EllcqPZTqw?typeid=158
https://www.boca.gov.tw/cp-220-5081-c06dc-2.html
