The Internal Revenue Service (IRS) breach that took place in May could now affect more than 300,000 taxpayer accounts, the agency said in a statement Monday.
The IRS said a deeper look at the breach indicated that hackers may have gained access to an additional 220,000 taxpayer files. "The IRS has identified more questionable attempts to obtain transcripts using sensitive information already in the hands of criminals," the statement said.
The agency said it start mailing notification letters "to about 220,000 taxpayers where there were instances of possible or potential access to 'Get Transcript' taxpayer account information" and, in an abundance of caution, to about 170,000 other households saying their data "could be at risk even though identity thieves failed in efforts to access the IRS system."
The IRS reported in May that about 114,000 files were compromised when hackers used social security numbers and other personal information to access old tax returns through the tax agency's Get Transcript system.