Fetching details from the dictionary...

yours sincerely; sincerely yours; yours truly
正式な手紙では最後に敬具と記すのが作法だ。
In formal letters, it is proper etiquette to close with a formal sign-off.
正式な手紙の結びには敬具と書くのが礼儀です。
I wrote 'sincerely yours' at the end of the letter.
拝啓で始めた手紙は敬具で締めくくるのが基本だ。
A letter that begins with a formal salutation should end with a formal closing.