1NT Forcing

1NT Forcing (aka the Forcing Notrump) is a cornerstone of the 2/1 ("Two Over One") bidding system. After partner opens 1/, a 1NT response shows 6-12 HCP and is a one-round force.

In standard bidding methods, a 1NT response shows 6-10 HCP. Playing 2/1, however, this range must be widened to include the game-invitational 11-12 point hands that are ineligible for a game-forcing 2/1 response. Note that a natural 2NT response is unavailable as well; it is reserved for the Jacoby 2NT convention that shows a game-forcing raise.

Examples of hands that would bid 1NT in response to 1:

Q52 93 A432 J987		Balanced, 7 points. A 1NT response in any system.
K98 J5 532 AK986		With 11 points, this hand is too weak to respond 2 in the 2/1 bidding system.
95 A52 54 T97652		This one is a matter of partnership discussion. Some players like to make crummy raises (4-5 points) via 1NT Forcing. In this case, responder plans to rebid hearts at the cheapest level.
K95 A52 K5 JT987		1NT Forcing can also be used to show a 3-card limit raise with 10-12 points. In this case, responder plans to jump-raise hearts next.

Frankly, this area is a weakness of the 2/1 system. A 1/ opening bid can be made on a wide variety of hand patterns between 11-20 points. Opener might not have a descriptive rebid available.

After 1 : 1NT

Opener's Rebid	Meaning
2	May be as short as two clubs, e.g. 4-5-2-2 shape with insufficient strength to make a 2 reverse.
2	May be as short as three diamonds, e.g. 4-5-3-1 or 3-5-3-2 shape.
2	6 hearts, rarely more. Might have a 4-card side suit.
2	4 spades, rarely 5 if opener is 6-5 in hearts and spades. This is a reverse showing at least 16 points.
2NT	Balanced, 18-19 points. Invites partner to bid 3NT.

All other bids are natural and/or a matter of conventional agreement.

After 1 : 1NT

Opener's Rebid	Meaning
2	3+ clubs, e.g. 5-3-2-3 shape and no other suitable bid.
2	3+ diamonds, e.g. 5-3-3-2 shape and no other suitable bid.
2	4+ hearts and 12-15 points.
2	6+ spades, may have a 4-card side suit.
2NT	Balanced, 18-19 points. Invites partner to bid 3NT.

All other bids are natural and/or a matter of conventional agreement.

1NT Semi-Forcing

Because of opener's potential rebid problems, some partnerships play 1NT as "semi-forcing", meaning that opener can pass with a minimum balanced hand. Many experts including Larry Cohen and Kit Woolsey endorse this approach. Another popular agreement is to play 1NT as semi-forcing only if responder is a passed hand.

After opener rebids 2

Responder's Rebid	Meaning
Pass	4+ clubs (typically 5), 6-10 points. Correcting to partner's major with doubleton support is preferable.
Any new suit	A new suit at the 2-level shows at least 5 cards, and poor support for partner's major. Non-forcing.
2-major	Signoff in partner's major, shows 2-card support or a very bad hand with 3-card support.
2NT	Balanced, 11-12 points. Invites partner to bid 3NT.
3	4+ clubs, 11-12 points. Non-forcing.
3-major	A 3-card limit raise.

After opener rebids 2

Responder's Rebid	Meaning
Pass	4+ diamonds (typically 5), 6-10 points. Correcting to partner's major with doubleton support is preferable.
Any new suit	At least 5 cards at the 2-level, or 6 cards at the 3-level. Non-forcing.
2-major	Signoff in partner's major, shows 2-card support or a very bad hand with 3-card support.
2NT	Balanced, 11-12 points. Invites partner to bid 3NT.
3	4+ diamonds, 11-12 points. Non-forcing.
3-major	A 3-card limit raise.

After opener rebids a major

Responder's Rebid	Meaning
Any new suit	6+ cards, and poor support for partner (a singleton or void). Non-forcing.
2NT	Balanced, 11-12 points. Invites partner to bid 3NT.
3-major	2-card support with 10-12 points or 3-card support with 10-11 points. Invites partner to bid game.
4-major	3-card support with 11-12 points.

After opener reverses

These rebids are used when opener opens 1 and rebids 2.

Responder's Rebid	Meaning
2NT	Balanced, showing 6-9 points. Non-forcing.
3/	6+ cards, non-forcing.
3	2-card support, or a very bad hand with 3-card support. Responder may have something as unsuitable as 2-2-5-4. Non-forcing.
3NT	10-12 points, balanced.

After opener rebids 2NT

Responder's Rebid	Meaning
Any new suit	6+ cards in that suit. Note that this is less preferable to simply bidding 3NT if possible.
3-major	A very bad hand with 3-card support. Non-forcing.
3NT	Signoff.

If the opening 1/ bid is doubled or overcalled, then a 1NT response is natural, 6-10 points and non-forcing. Against an opposing takeout double, responder can redouble with 11-12 balanced points.

If 1NT is doubled, then the force is "off." Opener can make a natural rebid or simply pass with an awkward hand pattern like 3-5-3-2. Opener may also choose to redouble to show extra strength.

		Opener			Responder
		KT93			AJ5
		AKJ62			54
		J3			K985
		42			JT63
		Opener 1 2 (2) Pass			Responder 1NT (1) 2 (3)

1. 1NT Forcing
2. Stuck for a bid. Lacking the strength to bid spades (and not playing Flannery).
3. Taking a preference. Raising clubs would promise game-invitational strength.

		Opener			Responder
		AT9852			KJ
		AK5			842
		K42			AQ85
		4			J963
		Opener 1 2 (2) 4			Responder 1NT (1) 3 (3) Pass

1. 1NT Forcing
2. Natural, 12-15 points and 6+ spades
3. Inviting game with doubleton support and a maximum

		Opener			Responder
		QJT95			K2
		AK54			QJT3
		Q4			A853
		84			976
		Opener 1 2 (2) Pass			Responder 1NT (1) 3 (3)

1. 1NT Forcing
2. Natural, 12-15 points and 4+ hearts
3. 4-card support and a maximum

		Opener			Responder
		K8653			9
		AK5			QJ6
		Q4			AJT532
		J65			974
		Opener 1 2 (2) Pass			Responder 1NT (1) 2 (3)

1. 1NT Forcing
2. Stuck for a bid. Shows 3+ clubs. (E.g. 5-3-2-3 shape.)
3. 5+ diamonds, 6-10 points, non-forcing

		Opener			Responder
		987			A62
		AQ873			K54
		AK4			Q763
		JT			K72
		Opener 1 2 (2) 4			Responder 1NT (1) 3 (3) Pass

1. 1NT Forcing
2. 3+ diamonds
3. A delayed jump raise, i.e. a 3-card limit raise