Regulations on the Permission and Administration of the Employment of Foreign Workers Article 12

When the period of stay of foreign workers referred to in Article 5 is 31 days or more but 90 days or less, the employer is required, in accordance with Article 9, to apply for a per-mit within 30 days of the worker arriving in the Republic of China.
中文原文 雇主聘僱外國人許可及管理辦法第12條
第五條之外國人,其停留期間在三十一日以上九十日以下者,得於該外國人入國後三十日內依第九條規定申請許可。

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