A claim or (concession) is a statement that your side will win a certain number of tricks without actually playing them out.

A claim should be accompanied by a clear statement of your ‘line of play’, i.e. the order in which remaining cards will be played. (You can’t just say, “The rest are mine” even if it is obvious.)

It is done as a courtesy to the opposition, and the Laws encourage it.  Indeed, the etiquette Law expressly discourages “prolonging play unnecessarily for the purpose of disconcerting an opponent”.  There is no benefit in waiting for the opposition to make discards when they can never win another trick.

Play ceases immediately the claim is made, unless all four players agree to continue.  If there is any doubt or the line of play is not stated, call the Director.  Any doubt about a claim is resolved in favour of the opposition.

Some players don’t like claims.  They think they are being cheated.  This is hardly ever the case, although occasionally a player may make an incorrect claim in all honesty.  You should always just politely check that the claimer is correct.  If you disagree with the claim you should call the Director.  

LAWs 68-71 Claims and Concessions

NZB Manual interpretations Flowchart - Disputed Claims

Some recommendations :

• Wait until all trumps have been played before claiming.    There is a specific Law about claiming when there is an outstanding trump (Law 70C) and any dispute will be ruled against the claimer.

• Don’t claim until you have only 3 or 4 cards remaining in your hand.

• It's best to claim when you have all winners in one hand, rather than having to explain the entries between the hands.  If you have to unblock or overtake in a suit, maybe it's best to just play a few more rounds to demonstrate.

• Lay your cards on the table one-by-one in the order that you intend to play them, stating what you are going to do.

• Don't concede as Declarer when you have a possibility of getting a lucky trick at the end, play it out, the defenders may keep the wrong cards.

• Don't give up and concede when you are a defender.   You don't know what your partner has.    

• If your partner concedes, you are allowed to immediately disagree (Law 68B2).   Of course this might help declarer guess the missing cards.

• If you think the opposition may have revoked earlier in the hand, you are allowed to ask to see their cards to check.   Or just play it out.

• If dummy is good and Declarer says "they're all good", they need to have an entry to dummy.    ALSO, Declarer should show ALL their cards, just to show that they have not revoked earlier.