Write 'respectfully yours' at the end of the letter.
Tips
culture
此致敬礼 is the standard formal letter closing in Chinese. 此致 goes at the end of the letter body, and 敬礼 goes on a new line. It's equivalent to 'Sincerely' or 'Respectfully yours' in English.
usage
Format: the body of the letter ends, then '此致' on its own line (sometimes at the end of the last paragraph), followed by '敬礼！' on the next line, indented two spaces.
