4NT as an ask for aces - 3 versions are used:

• Blackwood 0123 (regular):

• 5♣ - 0 or 4 aces;

• 5♦ - 1 or 5 aces;

• 5♥ - 2 aces;

• 5♠ - 3 aces.

• Blackwood 0314 (Roman Key Card Blackwood):

  • • 5♣ - 0 or 3 aces;

    • 5♦ - 1 or 4 aces;

    • 5♥ - 2 aces;

    • 5♠ - 2 aces + queen.

• Blackwood 1430 (Roman Key Card Blackwood):

  • • 5♣ - 0 or 3 aces;

    • 5♦ - 1 or 4 aces;

    • 5♥ - 2 aces;

    • 5♠ - 2 aces + queen.

If the queen of trump has been shown or no implied suit then:

• • • the next free bid or 5NT is an ask for kings.

otherwise:

• • • the next free bid is an ask for queen:

      • • back to the agreed suit - no trump queen;

        • any suit - the trump queen and the king;

        • 4NT/5NT -  the trump queen and no lower kings;

    • the second free bid or 5NT is an ask for kings.