Interpublic disclosed last Friday that it needed more time to file its 10-K form with US financial watchdog the Securities and Exchange Commission (SEC) because of problems with 'documentation and control of the financial results reporting process'.
The company has also asked its banks and bondholders to waive or change their loan agreements.
At the end of each fiscal year, US-listed companies must give the SEC their 10-K form, an audited document sent to shareholders reporting financial results and commenting on the outlook for the future.
Interpublic said it would not meet the 31 March deadline after discovering that it 'may have improperly consolidated the results of acquired companies'.
It has identified $145m (£76m) in revenue and $25m of net income that 'may have been improperly recognised from 1996 to 2001'.
Chief executive Michael Roth insisted the review would not affect the firm's businesses. Interpublic was due to update investors this Thursday (17 March).