[Raja1943]

In a semi-final qualification teams match at my club a hand was played in 4S and was set by one trick.The score was entered and next board was placed at table.
One of the players ,actually the partner of the declarer,claimed a revoke on the previous board and the TD ruled that the score should be corrected ,thus changing the score to contract made because of the revoke.It was a huge swing since at the other table the contract was one down.The TD said that a player could go back to 3 boards(hands) and claim a revoke.His decision caused a dispute and I was asked to state my ruling .I explained to the players involved that I needed some time to ask for help at BBO forum since I have no idea what the Law says and which Law to quote. All help is greatly appreciated .
Raja1943

[david_c]

Law 64B said:

No Penalty Assessed
The penalty for an established revoke does not apply:
...
4. After Non-offending Side Calls to Next Deal
if attention was first drawn to the revoke after a member of the nonoffending
side has made a call on the subsequent deal.

This seems to be the relevant Law. It sounds like the declarer's partner pointed out the revoke in time, so they get their extra trick. The fact that the score was agreed does not make it too late (but it would have been more helpful to point out the revoke at that point!) There may be a problem, however, if the defenders do not agree that a revoke occurred. If the TD is unable to decide what happened, then the defenders may get the benefit of the doubt because dummy could have pointed out the revoke before the cards were put away.

You might also like to quote:

Law 9A2b1 said:

Dummy may not call attention to an irregularity during the
play but may do so after play of the hand is concluded.

Your TD seems to be wrong in saying that a revoke can be claimed up to three hands later. In this case it would be too late to apply the one- or two-trick penalty for a revoke. However, if the revoke caused the non-offending side to win fewer tricks than they would otherwise have done, then this Law would apply:

Law 64C said:

Director Responsible for Equity
When, after any established revoke, including those not subject to
penalty, the Director deems that the non-offending side is insufficiently
compensated by this Law for the damage caused, he shall assign an
adjusted score.