Opening 1NT with a singleton: It’s officially legal

The ACBL Board of Directors removed a legal gray area surrounding semi-balanced notrump openers when it approved a change to the definition of a notrump opening in the General Convention Chart. The change allows players to open 1NT with hands that include a singleton ace, king or queen, as long as they do not also contain a doubleton.
Here is the new definition, effective Aug. 1:
“A notrump opening or overcall is natural if, by agreement, it contains no void, at most one singleton which must be the A, K or Q and no more than two doubletons. If the hand contains a singleton, it may have no doubleton.”
This includes hand patterns such as 5-4-3-1, 6-3-3-1 and 4-4-4-1, in addition to those that were previously allowed, such as 4-3-3-3, 5-3-3-2 and 5-4-2-2.
The change was recommended by the Competitions and Conventions Committee, a group of players appointed by the Board, in an effort to bring regulations in line with popular and expert practice, said ACBL Field Manager Sol Weinstein, who supervises tournament directors.
Before, opening notrump with a singleton was considered a psych. It was legal to do, but players could not have an agreement to open such hands 1NT or 2NT. The lack of clarity was a thorny issue for directors.
“Many players were doing it anyway,” Weinstein said, particularly when a different opening would create a problematic rebid. “They decided it’s not right to have a rule that’s contrary to the way bridge is being played.” The idea of expanding the definition has been discussed for years within the committee, but previous proposals have failed because they lacked the simplicity of the new definition.
“The Laws don’t allow you to limit bridge judgment,” Weinstein explained. “Regulations have to conform to the Laws.”
The new definition prohibits opening notrump with more shapely hands, such as 5-5-2-1, 6-4-2-1 or 7-22-2. “All of this has to do with your agreements,” Weinstein noted. “That doesn’t prohibit an out-andout psych, but you can’t keep doing that or it becomes an agreement, and an illegal one at that.”
The change does not impact the one allowable exception of a partnership agreement where 1NT is treated as a 100% forcing opening bid (and not considered “natural” with any distribution). The use of such an unbalanced, non-natural 1NT opening must be alerted.