But company confirms they will bel based on performance
Aon is pressing ahead with payment of bonuses, but has reduced the sums for some employees.
The broker, which began to pay the bonuses at the end of last month, said they would reflect the harsh economic environment.
But an Aon spokesman said the company was not imposing a uniform reduction and bonuses were still based on performance.
In previous years, some bonuses have been the equivalent of 10% of salary.
The move has come at a time when some big brokers are imposing cutbacks.
Willis, for example, has offered staff unpaid leave as it looks to slash costs across the group, while Marsh and Aon last year announced plans to cut hundreds of jobs.
In February, Aon posted a 35% drop in net income for the fourth quarter of 2008. Net income was $123m (£82.5m).