complimentary close

or complimentary closing

[klohz or kloh-zing]
  1. the part of a letter that by convention immediately precedes the signature, as “Very truly yours,” “Cordially,” or “Sincerely yours.”

Origin of complimentary close

First recorded in 1915–20
Also called closing, close. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018