The company blamed a computer error for failure to properly account for the deal.
It also warned that heads might roll and that the position of its auditors would be reviewed.
Salomon revised its fourth-quarter 1994 loss to $157m from a loss of $122m.
Losses for the year are now $399m, against the previously stated $364m.
The restatement is due to an extra $35m tax charge on the yen deal, which the company thought it had accounted for in 1991.
The company said the miscalculations were because a computer did not accurately distinguish between interest income and principal gains and losses upon the redemption of a number of non-dollar securities, principally Mexican Tesobonos and Cetes.
Salomon said that the mistake would have no serious impact on finances, but an investigation was under way and those responsible would be dealt with.
Salomon's chief executive, Robert Denham, said: "Nothing is more important to this company than an absolute insistence on the highest possible standards of control and of accuracy in reporting.
"We will therefore accelerate the implementation of a variety of steps to strengthen our financial reporting and control procedures.
"We are also making appropriate changes in financial division and operations personnel. Finally, our external auditors have stated to us that these items were not uncovered in prior year audits.
"Accordingly, the board will look with particular care this year at the designation of outside auditors."
It is understood that Arthur Andersen is the company's main auditor.