Interference Over 1C Opening Bid
   

Over a double if non-specific
......Pass= 0-4 hcp
......1D= 5-7 hcp
......XX= Game force, balanced
......All other bids, unchanged

Over a double = both majors
......Cue bid= 8+ hcp w stopper in other major
......1NT= 8+ w stoppers in both majors
......XX= 8+ hcp w/o major stopper
......Other bids, unchanged

2nd level interference
......Lebensohl

After 3 Level Overcall
......X= Balance, pos response, no upper limit
......Suit bid= Positive, game force
......3NT= 8-11 with stoppers

After 4 Level Overcall
......X= offensive and defensive values

Over suit interference
......Pass= 0-4 hcp;
......X= 5-8 hcp unbalance then bid suit or 5+ balanced
......New suit= 8+ hcp and 5+ cards, game forcing
......Cue bid their suit= GF values, balance, w/o stopper

Over 1NT, showing minors
......X= 6-10 or 13+ hcp, can penalize at least one of their suits
......2C= 5+ Hearts, GF
......2D= 5+ Spades, GF
......2H= 5+ Hearts, invite
......2S= 5+ Spades, invite


Higher level interference and general principles

X by opener at 1/2 level is forcing one round
X at 3 level is game forcing
After take out X by responder, next X by either opener or responder is alway take out
Third X is for penalty, as are all that follow