Morgan Stanley and Goldman Sachs Group Inc. both decided lastmonth that it was worth losing millions of dollars in fees to getcredit on a big merger they didn't work on, four people withknowledge of the matter said.

The investment banks asked for credit in league tables—rankingsof advisers on mergers and acquisitions (M&A) maintained byboth Bloomberg LP and Dealogic—for working on the $25 billion saleof Forest Laboratories Inc. to Actavis Inc. last month. Neitheractually had a role on the deal, said the people who asked not tobe identified discussing confidential information.

Instead, the two banks, using previous contracts with Forest,negotiated to get credit for the deal in exchange for millions ofdollars in fees they were owed, the people said. The contracts hada clause, commonly known as a tail, that entitled them to fees evenif the company was sold by another bank, they said. After the dealwas announced they each agreed to cut the fees they were due inexchange for being able to claim the league-table credit.