4th Suit Forcing

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On the auction below which hand does North have for their jump to 3♠? If 3♠ shows hand 1, what should North bid with hand 2 which has invitational values? If 3♠ is invitational, what should North bid with the game forcing values of hand 1?

On the auction above, South has a wide range 12-17 points. So North must strive to keep the auction open if a game may be available. Even if North is weak and a game isn’t available, North may have a preference for another suit. So a 2♠ rebid doesn’t show invitational values, it simply shows 5+ spades and a desire to improve the contract. To show invitational values with 5+ spades, North jumps to 3♠ (hand 2).  

North shouldn’t jump to 4♠ with hand 1 for several reasons:

1. North doesn’t know whether South has 3-card spade support. Another strain may be better.

2. Even if South has 3-card spade support, a jump to 4♠ consumes bidding space needed to assess whether a slam is available.

Responder has plenty of invitational bids available.  On the above auction below, responder can bid a natural 2NT, 3♣, 3♦, or 3♠ to invite game.  When responder has a game forcing hand, they need an easy reliable way to establish a game force.  

 
4^th Suit Force provides an easy way to establish a game force, look for the right strain, and assess whether a slam is available. After 3 suits haven been bid without a jump, responder’s bid of the 4^th suit is artificial and game forcing. Bidding proceeds naturally. Playing 4^th Suit Forcing, North’s rebids 2♥ with hand 1.  North’s 2♥ bid is artificial and game forcing.

 
South rebids naturally. With 3-card spade support, South bids 3♠. With 4 hearts, South raises hearts. Otherwise, South can bid 2NT with a heart stopper. Lacking a heart stopper, South will rebid their longer minor. South will rebid clubs with 5-5 in the minors.  Sometimes all of South's rebids are lies.  It is important for partnerships to agree on which bid is used with a hand that doesn't have an honest rebid.  Without an agreement, all of South's rebids are suspect.  See our article on Punt Bids for our recommendations.  

If North had jumped to 3♥, a jump in the 4^th suit, it shows a good 5-5 invitational hand (e.g. ♠KQ752 ♥AJ962 ♦84 ♣7).

There is one auction where the 4^th suit can be bid at the one level.  This auction requires discussion with your partner.

Some partnerships plays a 1♠ rebid by responder as 4^th Suit Forcing, an artificial game force.  Others use a jump to 2♠ as 4^th Suit Forcing.  We recommend using the jump to 2♠ as 4^th Suit Forcing.  This allows a responder with 4 spades and less than game forcing values to rebid 1♠ to look for a spade fit.  Responder's 1♠ rebid is natural and forcing for one round.  The 4^th Suit Forcing jump to 2♠ doesn't deny holding 4 spades, opener should bid 3♠ if they have 4 spades.  

Please discuss this auction with your partner to ensure you have a firm agreement.  

Continuations after 4^th Suit Forcing

Opener describes their hand after responder's 4^th Suit Forcing artificial game force.  Opener's options include:

• Showing a stopper in the 4th suit by bidding notrump
  With just the Ace, a non-positional stopper, opener may prefer giving responding the chance to declarer a notrump contract to protect a positional honor.
• Showing 3-card support for opener's suit
• Bidding the 4th suit at the 3-level to show 4 cards in the suit
• Rebidding a suit to show extra length

Sometimes opener's hand will not fit any of the available bids.  Read our Punt Bids article to learn what opener should do when no good bid is available.  

The auction continues naturally, looking for the right game.  When choosing which game to play, you will generally want to follow the priorities below.

1. Choose a major suit game with an 8+ card fit.
2. Otherwise, choose 3NT if feasible.
3. If not feasible, consider playing in 4♥ or 4♠ in a 7-card fit.
4. If not feasible, fallback to game in a minor.

5♣ and 5♦ are the games of last resort because they require 11 tricks and pay only 20 points per trick.  

When 4^th Suit Forcing Applies

4^th Suit Forcing is off when the opponents bid a suit. Use a cue bid of the opponent’s suit to force. 4^th Suit Forcing is off after a jump bid. 4^th Suit Forcing doesn’t apply in a 2/1 Game Force auction. A bid of the 4^th suit is typically natural or a notrump probe. A bid of the 4^th Suit by a passed hand is natural and non-forcing. If you play XYZ, 4^th Suit Forcing doesn’t apply when 3 suits have been bid at the 1-level. XYZ takes precedence.

When an uncontested auction begins 1♣ - 1♦ - 1♥, it is common to play a 1♠ rebid by responder as natural and forcing, but not forcing to game. Many partnerships use a jump to 2♠ as 4^th Suit Forcing, an artificial game force. That is our recommendation, but it requires discussion with your partner.

Jumps in the 4^th Suit

We recommend treating a jump in the 4^th suit as a natural and invitational showing at least 5-5 distribution.  

On the above auction, North is showing a game forcing hand with 5+ hearts and longer spades.  North might have a hand like  ♠KQ752 ♥AJ962 ♦84 ♣7.

Simlarly, a 4^th suit jump in a minor suit is also a natural and invitational with at least 5-5 distribution.  

On the above auction, North is showing a game forcing hand with 5+ hearts and 5+ clubs.  North might have a hand like  ♠83 ♥KQ962 ♦4 ♣KQ872.
Note:  Many partnerships prefer using the 4th suit jump in a minorto show a weak hand with a long minor.  It is important to discuss this with your partner.

The meaning of a 4th Suit Jump in spades depends on whether you use 1♠ or 2♠ as 4^th Suit Forcing.

If you play a jump to 2♠ as 4^th Suit Forcing, North jump to 2♠ is an artificial game force.

If you play a 1♠ response as 4^th Suit Forcing, North's jump to 2♠ is a jump reverse by responder.  So it should be natural and game forcing showing a very distributional hand.  North might have a hand like ♠KQ873 ♥2 ♦AQ9642 ♣J.

Please discuss this with your partner and make sure you have a firm agreement.