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This article was prompted by receipt of a query from a club member. I sense that it refers to a point that many players have interest in.

Can you put me right on Mechanical Errors please? Up to what point can such a bidding error be corrected? I have been known to pull out a bid then gaze round the room before I realise it is incorrect. By that time the next player has bid. I am then in the realms of psyching!!


A bid may be substituted if:

  1. It is a correction (of a 'mechanical error') rather than a change of mind, AND

  2. The substitution is made – or attempted – as soon as the offender realises the mistake, AND

  3. All this happens before the offender’s partner calls and before the end of the auction


This situation is covered by Law 25A and Orange Book paragraph 7 B 8, which have been reproduced below. Note that the word ‘Call’ includes ‘Pass’, unlike ‘Bid’, which does not. Note also that the Laws do not use the term ‘mechanical error’, but rather ‘unintended call’.


A Unintended Call

1 Until his partner makes a call, a player may substitute his intended call for an unintended call but only if he does so, or attempts to do so, without pause for thought. The second (intended) call stands and is subject to the appropriate Law

2 No substitution of call may be made when his partner has made a subsequent call.

3 If the auction ends before it reaches the player’s partner no substitution may occur after the end of the auction period (see Law 22)

4 If a substitution is allowed the LHO may withdraw any call he made over the first call. Information from the withdrawn call is authorised only to his side. There is no further rectification.

B Call Intended

1 A substituted call not permitted by A may be accepted by the offender’s LHO. (It is accepted if LHO calls intentionally over it.). The first call is then withdrawn, the second call stands and the auction continues

2 Except as in 1 a substitution not permitted by A is cancelled. The original call stands and the auction continues.

3 Law 16D applies to a call withdrawn or cancelled.


Law 16D refers to authorised / unauthorised information resulting from the cancelled call

Law 22 defines the end of the auction period – basically that is when the opening lead is faced.

The Orange Book

The “Orange Book” gives an EBU interpretation of all this, which is particularly set in the modern context of using Bidding Boxes rather than verbal calls:

7 B 8 Calls made using (bidding box) cards are treated under the Laws in the same way as spoken calls. For example, a call may be changed without penalty under Law 25A only if:

(a) The change is solely due to the player having taken out the wrong card in error, AND

(b) He changes – or attempts to change – it instantly after he REALISES that he has removed the wrong card by mistake


So, for example, supposing that a player suddenly ‘wakes up’ after he has pulled out the Pass card and wants to do something else - that is ‘tough cheese’ – the pass has to stand because the desired action represents a change of mind, not correction of an accidental error, and the Offender's partner has to be careful not to draw unauthorised information from partner's attempts to substitute a bid.

There is no hard and fast definition of ‘mechanical error’, but usually if it was the card next to the one intended it would be allowed, For example, a bid of Pass-3NT could very likely be changed to Stop-3NT if that was clearly what was intended. It is the advent of bidding boxes that has really given rise to this issue – e.g., nobody would speak ‘Pass-3NT’ when they intended to say ‘Stop-3NT’, and nobody would actually say '1H' when they thought they were saying '1S' or '2H'.

The word ‘REALISES’ is critical, and it is easier to judge than the phrase 'without pause for thought' that the Law uses. So, turning back to the original query, the reference to 'gazing around the room' wouldn't necessarily be interpreted as 'pausing for thought'.

Given the reference to ‘psyches’ in the original query, it should be pointed out that there is no danger of an uncorrected ‘mechanical error’ being treated as a psyche, e.g., see 6A1 in a psyche is a ‘deliberate’ inappropriate bid, whereas an uncorrected 'mechanical error' would be treated as a misbid.

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