Most players have at one time or another fumbled with the bidding box and a different call to the one you intend ends up on the table. Perhaps the bidding cards are old and stick together or your fingers pick up the wrong card so instead of 1S you look down to see that 1NT is there. Under Law 25A providing you attempt to change it without pause for thought then the TD will let you change. What does ‘pause for thought’ really mean? Many people think it means ‘in the same breath’ and that is not correct. The ‘pause for thought’ can only begin when you realise it is wrong, so a sharp intake of breath or a guffaw when you realise is usually enough to signal that you want to change it. Players often call this ‘mechanical error’ although the correct term is ‘unintended call’.
Changes of mind are NOT normally allowed; so “1NT” “pass” “2H, oh no I mean 2D because I forgot I was playing transfers” is not an unintended call.
But what about if partner wakes you up?
You put down, what you think is, 1S and partner says “12 to 14”. You think ‘silly old fool’ but then when you look down you see the 1NT on the table.
Are you allowed to change it under Law 25A?
Many people are not aware that in December 2011 the World Bridge Federation (who draft the laws) added a footnote to Law 25A as follows:
A player is allowed to replace an unintended call if the conditions described in Law 25A are met, no matter how he may become aware of his error.
So partner announcing 12 to 14 is enough to wake the player up and the TD would allow the change – providing the TD is completely satisfied the original call was inadvertent and unintended.
Club TDs should ensure that they write the footnote into their Law Books – there is a space on the previous page which looks like it was made for it.