Enforcement Rules of the Income Tax Act Article 21

Regarding Subparagraph 1, Paragraph 1, Article 17 of the Act that governs application of the amount of tax exemption for dependents, where children of the taxpayer or siblings of the taxpayer or his/her spouse that attained the age of majority and are enrolled in school or supported by the taxpayer due to physical or mental disability, the taxpayer shall submit the school enrollment certificate or a copy of the handbook for the disabled and mentally retarded specified or other such recognized proof issued by the relevant government organization, or a copy of a medical diagnosis issued by a specialist physician as required in Paragraph 1, Article 19 of the Mental Health Act.
中文原文 所得稅法施行細則第21條
本法第十七條第一項第一款關於減除扶養親屬免稅額之規定,其為納稅義務人之子女、納稅義務人及其配偶之同胞兄弟姊妹,已成年而在校就學或因身心障礙受納稅義務人扶養者,納稅義務人於結算申報時,應檢附在校就學之證明或社政主管機關核發之身心障礙手冊或身心障礙證明影本,或精神衛生法第十九條第一項規定之專科醫師診斷證明書影本備核。

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