The licence conditions allows the department to conduct special audit of telecom operators whenever required.
"DoT is evaluating the option of auditing the accounts of telecom firms after 2008. It is a routine thing as per the licence conditions," a source in DoT said.
The source further said no timeline has been finalised yet for the audit.
The department had earlier conducted the audit for assessment years 2006 to 2008.
Show cause notices to five private operators including Bharti Airtel and Vodafone amounting to about Rs 1,637 crore were issued for under reporting revenues.