Inverted minor raise

When responder bids 2 of the opening suit over a 1C/1D opening, it is forcing for one round and both sides know that there is no hope for a major fit. This is known as inverted minor raise (IMR). The priority would then shift to the possibly of playing in NT. Opener may rebid as follows:

Bid	Meaning	Responder's continuations
new suit (!!)	Stopper-asking	Rebid opening suit (no stopper) or bid NT (with stopper)
2NT	12-14 balanced	Pass or raise to 3NT or Gerber Rebidding opening suit shows unbalanced hand
3 of opening suit	Minimum hand and unbalanced	Pass 3 of a new suit (!!) -- stopper-asking
jump to new suit (!!)	HSST	See here
3NT	18-19 balanced	Pass or Gerber
1C > 2C > 4C	Gerber	See here
1D > 2D > 4D	17+	Raise to 5 of opening suit or HSST or Blackwood
4NT	Blackwood	See here
5 of opening suit	To play

If opponent overcalls after IMR (e.g. 1D > 2D > (2H)), the F1 ceases. However, if opener chooses to rebid, the above table still applies with the following adjustments:

• A pass usually shows a minimum hand without stopper in opponent's suit(s).
• A double is for penalty.
• Bidding 2NT or 3NT requires a good stopper in opponent's suit(s).
• Bidding 3 of the opening suit usually promises a good suit or above-minimum values.

If responder has passed before, opponent overcalls (below 2m) after 1m opening (before responder bids), and/or the 1m bid is an overcall rather than an opening bid, the IMR convention is still ON, i.e. bidding 2m shows a stronger hand than 3m. There are however some adjustments as follows:

Scenario	Example	Range of 2m	Is it forcing?*	What is a cue-bid?
Original system	1D > 2D	9+	Yes
Responder has passed	P > (P) > 1C > (P)	9-11	No
Opponent has bid after opener and responder has not passed	1C > (1S)	13+	Yes	10-12 points with trump support
Opponent has bid before opener and responder has passed	(1C) > 1D > (P) (1C) > 1D > (1S)	8-9	No	10-12 points with trump support
Opponent has bid before opener and responder has passed	P > (1C) > 1D > (P) P > (1C) > 1D > (1S)	8-9	No	10-11 points with trump support
Opponent has bid after opener and responder has passed	P > (P) > 1C > (1S)	8-9	No	10-11 points with trump support

* No matter whether 2m is forcing or not, if opener decides to rebid, the original IMR system is ON, i.e. a new suit (including cue-bid) is stopper-asking and so on. If opponent has bid, then opener bidding 2NT or 3NT would require a good stopper in opponent's suit(s).