Smith Barney promised a lawyer to discount its standard commission rates to as little as three cents a share.  It in fact billed him more than its standard rates.  The lawyer demanded, and got, an accounting.  But Smith Barney's calculations showed the delta between standard rates and actual rates — not the difference between three cents and actual rates.  The numbers thus understated the overcharge, likely by a lot.

And yet the lawyer signed the settlement papers that Smith Barney sent him hours after delivering the overcharge calculations, which he didn't study until a day or so later.  When he saw the error, he asked SB to hold the settlement "in abeyance" (possibly a village in France).  The brokerage refused.  Both sides sued.  Smith Barney won.

The First Circuit affirmed.  Citibank Global Markets, Inc. v. Santana, No. 08-1533 (1st Cir. July 17, 2009).  As Judge Howard summarized:

In this appeal from the dismissal of a counterclaim, the appellants ask us to either set aside or reform a settlement agreement between two sophisticated parties because the circumstances of the negotiation carry a whiff of unseemliness, and there has been a suggestion of fraud.  Considering all of the facts and circumstances surrounding the negotiation, we conclude that the settlement agreement is binding under Puerto Rican law, and we  detect no fraud or absence of disclosure that justify unraveling or disturbing the agreement.

Id., slip op. at 1.