Checkback Following Opener's 1NT Rebid

Overview

If opener rebids 1NT following responder's 1-level response, 2♣ from responder is checkback. It is an artificial, Stayman-like bid, designed to elicit further information about opener's hand, with particular emphasis on the major suits. Note that if responder has no interest in opener's major-suit holdings, and simply wants to invite 3NT, he/she simply bids 2NT - using 2♣ in this situation simply provides the defence with unnecessary information.

As with Stayman in response to a 1NT opening bid, responder can only use checkback if he/she is in a position to handle any response from the opening bidder.

As far as the major suits are concerned, opener is being asked to show length of which responder is so far unaware, i.e.

• if the opening bid was 1♥, opener would now rebid 2♥ [minimum hand] or 3♥ [maximum hand] to show a 5-card suit [doesn't deny three spades]
• if the opening bid was 1♣/1♦ and responder bid 1♥:
  -   2♥/3♥ would show a 3-card suit in a respectively minimum/maximum 15-17 hand
  -   2♠/3♠ would show two hearts and four spades in a respectively minimum/maximum hand
  -   2♦/2NT would deny either three hearts or four spades in a respectively minimum/maximum hand
• if the opening bid was 1♣/1♦ and the initial response was 1♠, now over 2♣ checkback:
  -   2♥/3♥ shows four hearts in a respectively weak/strong 15-17 hand [doesn't deny three spades]
  -   2♦/2NT denies four hearts or three spades in a respectively weak/strong 15-17 hand
  -   2♠/3♠ denies four hearts but shows three spades in a respectively weak/strong 15-17 hand.

Note that where responder has shown a heart feature and therefore not denied a spade feature, responder can go to to show his/her own 5-card spade suit.