Aon has warned its earnings would fall short of expectations for the first quarter and for the full-year.
The Chicago-based broker, the world's second biggest, is being hit by higher than expected payroll costs after several years of acquisitions.
Its shares fell by nearly 6% on 19 April, the day of the announcement, as a result.
Aon said it expected first-quarter earnings to be between 46 and 49 cents (31.8p and 33.8p) a share, excluding a one-time income item of 11 cents (7.6p) per share from a tax settlement.
A survey of analysts by Thomson Financial/First Call found they had expected to see Aon earn 55 cents (38p)a share.
The company also said full-year earnings per share would be towards the bottom of a $2.30 to $2.75 range (£1.59 to £1.90), compared with the consensus estimate of $2.53 (£1.75).
