What does 'claim' mean?

You claim when you're certain of the number of tricks you're going to win on a hand – in other words, when there's no need to play on. 

Here's a cast-iron example. You're sitting South, playing in 3NT, and EW started by taking the first two tricks with the ♣A and ♣K. It's pretty clear that you're going to take the rest of the tricks: you have the top club, two tricks each in spades and hearts and 6 diamond tricks – even if the diamonds are 4-0 you can clear them with your ♦AKQJ. It's a no-brainer.

To insist on 'playing the hand out' is merely to waste the other players' (and your own) time. So to save time (a precious commodity in a BBO pairs game) and to save your opponents the pointless exercise of trying to decide what discards to make on your diamonds, you claim.

Do I HAVE to claim?

Well, the law book says you should if it's appropriate – but it's only appropriate if you're sure. Inexperienced players are often nervous about claiming, as they need more practice at 'predicting' how the cards are going to play out. But playing on BBO is a great way of developing this skill – both when claiming and when deciding whether or not to accept a claim. We'll see how it works below. Meanwhile, while still on this hand ...

Supposing we're in 5 ♦ instead of 3NT?

Now you're not in a position to claim – yet. That's because the opponents' next lead (probably another club) might get ruffed. You're going to wait till you have the lead again until you make your claim. And even then, just to make things absolutely crystal clear, you'll explain that you're 'clearing trumps' before you do anything else. 

How do I make a claim?

1   You click on the  Claim  button on the left of the screen. This brings up a panel like that shown left.

2   Click on the number of further tricks you're claiming.
     (Here the claim's being made very early - after trick 1! Declarer can see that she's worth just 7 more tricks and has no chance of making any after that.)

3   (Optional) If you think it's necessary, you can clarify your claim by typing in the Explain line. Typically, this explains how you're going to play it – examples might be Cross-ruffing or Ruffing losing spade in dummy or Discarding club on AD. Or it might just say Give you the AC.
     Here, declarer's writing 'Drawing trumps' so the opps know they're not going to get a ruff!

4   Now click on  Claim  and the claim will appear on your opponents' (and partner's) screens.

See below for what happens next ...

What happens when an opponent claims?

You see a yellow 'claim' box on the left of the screen. At the same time, what's left in all four hands are now displayed so that you can decide whether to accept the claim or not.

Sometimes, as we saw above, there's a short explanation to accompany the claim eg Drawing trumps. In the example shown here, there's no added explanation.

When is the claim accepted?

Only when both you and your partner have clicked on the  Yes  button. If you're happy with the claim don't forget to accept it – otherwise you'll keep everyone hanging around waiting!

If either you or your partner clicks on the  No  button, the claim is rejected.

What happens if the claim is rejected?

Play continues as if the claim hadn't been made. 

 IMPORTANT  Please don't reject a claim out of hand: claims are made out of courtesy and to save time, and a valid claim rejected makes for bad feeling and wasted time.

Can defenders make claims too?

Yes, of course. Imagine that declarer in 3NT is stuck in dummy, which contains just ♥K543. and your last four cards are ♥A ♣AKQ. You're obviously going to take the last four tricks, so  Claim  them – no 'added explanation' necessary! 
(In this case, only declarer decides whether to accept the claim – dummy's opinion is irrelevant.)

What about concessions?

Well, a concession is essentially a claim of 0 tricks. Such claims are usually accepted!

If you're a defender, check that you're sure partner can take no more tricks before you press the button ...