In friendly games, the checking player customarily says "check '' when making a checking move. Announcing "check '' is not required under the rules of chess and it is usually not done in formal games. Until the early 20th century a player was expected to announce "check '', and some sources of rules even required it (Hooper & Whyld 1992: 74).
when do you have to say check in chess
Announcing "check '' is not required under the rules of chess