Roman Key Card Blackwood - 1430 version

RKCB is similar to Blackwood, but instead of four Aces there are Five Keycards. They are the Aces plus the King of the agreed trump suit. Starting with 4NT, a reply of 5♣ shows 1 or 4 Keycards, 5 shows 0 or 3, 5 shows 2 Keycards but no trump Queen, and 5♠ shows 2 Keycards with the trump Queen.
If your side has all five Keycards, bidding 5NT will repeat the process for Kings, remembering that there are only three Kings since the trump King is counted as a Keycard. There are two popular methods for responding to 5NT. The first is the same as normal Blackwood - 6♣ shows no Kings, 6 shows one, and 6 shows three. This is the method used in the recommended bidding here.
If the response to 4NT is 5♣ or 5 the 4NT bidder may choose to ask about the trump Queen rather than ask for Kings. She does this by bidding the cheapest non-trump suit. Partner denies the trump Queen by returning to the trump suit. A 5NT bid confirms the trump Queen, but shows no outside Kings. Bidding any non-trump suit confirms the trump Queen and also the King of the suit bid.
Void showing by Responder is handled just as in regular Blackwood except it refers to one or two Keycards, rather than one or two Aces.

Click any Deal to start.