The Forcing Notrump convention is an integral part of every 2-over-1 forcing-to-game system. It's used by responder to describe a wide range of hands that have less than game-forcing values (5-11 pts.). For guidelines that apply to other parts of this bidding system, see The 2-over-1 Bidding System.
If partner opens 1 or 1 and RHO passes, make your natural raise or 1-level response if available. With other hands, you can bid the Forcing 1NT to show:
If you play constructive raises (1 - 2 promises 8-10 support points), you can also use Forcing Notrump auctions to show weaker 3-card raises. In the auction 1 - 1NT - 2 - 2, responder is showing either a doubleton heart or 3 hearts with bare-minimum values (fewer than 8 support points).
After you open 1 or 1 and partner responds 1NT, you must bid again to allow him to complete the description of his hand. Your rebid will show your strength and tell partner something about your hand pattern. If you have extra length in your major or you hold a 4+-card side suit, you'll be making a natural, descriptive rebid. With many other types of hands, though, you may have to bid a 3-card minor. Here are your options for your rebid:
When you rebid your major or raise notrump, you pinpoint your high-card strength. Bids of new suits have a much wider range. After 1 - 1NT, your rebid of 2, 2 or 2 could be made with as many as 16-17 high-card points. Partner can pass these rebids, but if he has a good responding hand (9+ pts.), he'll often stretch to bid again to keep the auction open for you. This will allow you to show your extra strength if you have it.
Note that all the ranges and recommendations above are subject to your judgment of your hand's actual playing strength. You'll often want to evaluate a hand "up" if it has very strong suits and distributional values.
After 1 - 1NT, you have a dilemma when you hold a hand like KJ10854 K74 AJ83 3. Do you show your extra length in spades or do you bid the diamond suit?
If you have a bare minimum, you'll usually want to rebid your 6-card major, especially if your 4-card suit is a minor. This limits your point-count right away and simplifies the auction. If you have 6 spades and 4 hearts, it may be important to get the other major into the auction, so you can base your decision on suit quality. With weak spades and decent hearts -- a hand such as K108654 KQ93 42 A -- rebid 2.
With a powerhouse hand (18+ pts.), you can make a jump-shift into your second suit to force responder to bid again. The problem hand is one with moderate extra values (15-17 pts.). To show this strength, bid 2 of your 4-card suit and hope partner can bid again. If he does, you can then show your extra values by making a game-try bid.
For example, after 1 - 1NT, rebid just 2 with AQ9864 743 2 AJ82. If you instead hold AQ9864 A74 2 AJ82, rebid 2. If partner takes a preference to 2, you can invite game with 3. If he bids 2, you'll raise to 3. If he bids 2, you'll bid 2 to show your extra length and strength (partner will know you have extra values because with 6 spades and a minimum, you would have rebid 2 over 1NT).
After opener's rebid, you'll clarify your strength. You have several ways to describe hands in two different point ranges.
The Forcing NT is used only after partner opens 1 or 1. In the auctions 1 - 1NT and 1 - 1NT, responder's 1NT is standard (not forcing, 6-10 pts).
The Forcing NT is "off" in competition. If your RHO bids or doubles, your 1NT response reverts to its standard, non-forcing meaning (7-10 pts. with stoppers in the opponent's suit).
This summary recommends that a 1NT response is forcing for one round and denies forcing-to-game values. Some pairs choose to play the 1NT response as unlimited by an unpassed hand. Others play it as semi-forcing (opener can pass with a balanced 12 or 13 pts.). These are areas for partnership discussion.