noun
Honorific term used to refer respectfully to the addressee's letter. Formal and somewhat old-fashioned; in modern business correspondence, お手紙 or ご書状 are more common.
貴札、拝見いたしました。
I have respectfully read your letter.
Compound of 貴 (ki, 'noble; your') and 札 (satsu, 'tag; letter'). The exact historical derivation is uncertain, but the kanji combination conventionally expresses respectful reference to the addressee's written communication.