MAH JONGG IN ERROR WITH NO NEW EXPOSURES (Article 52) 

Commentary: When a player declares Mah Jongg in error and has not exposed concealed tiles, they can retract the declaration without penalty. This also applies if the player picks a tile from the wall and places it on the flat part of the rack, as long as they have not exposed concealed tiles.

Question from a player:  What happens if I declare mah jongg in error but do not expose my tiles? 

Answer from the NMJL:  If a player calls Mah Jongg in error and the mistake is rectified immediately, before the hand is exposed or before other players expose or disturb their hands, the game continues without penalty.

Source: Mah Jongg Made Easy (2024 pages 21 #2); call to the league (01/2024)

Other answers from the NMJL:

“If a player calls mah jongg in error and the mistake is rectified immediately before the hand is exposed and before any other player exposes or disturbs the hand, the game continues without any penalty.” 
 
Sources for other answers:  National Mah Jongg League Bulletin Q&A 1993 page 12