The Securities Commission says companies need to be upfront with investors about their financial health, in the economic downturn.
The regulator has looked at the financial statements of 24 companies with balance dates of between March and December 2008.
The commission says it is speaking to several firms after discovering what it calls inadequate book-keeping and has warned other companies to disclose more information.
Chair Jane Diplock says she's particularly concerned about how impaired assets are valued, as well as changes in funding arrangements and management compensation.
