Is there any requirement on the use of characters in applying for English .TW domain names?
(i) Applicant could use 52 English alphabets in either capital or small letters, numbers from 0-9, and hyphens (-), up to a total of 63 characters. However, the first and the last characters had to be English alphabets or numbers. In addition, no special symbols under RFC-1035 shall be used.
(ii) Requirement in the length of the characters: in each of the .TW Domain Name, there should be at least 2 characters, but no more than 63 characters.
Is there any difference in using capital letters of small letters for the .TW domain name in English?
Only small letters would be accepted for such application. Once approved, it would make no difference if the user key in .TW Domain Name in capital or small letters. Either the word written in capital letters or small letters would direct to the same URL or E-mail Address.
In case of any discrepancy between this translation and the original Chinese text, the Chinese text shall govern. Terms in this translation expressed in the singular should be construed as also including the plural, and vice versa.

Source: http://rs.twnic.net.tw/