Xerox says the amount of sales and revenues figures it will have to recalculate amounts to "less than $2 billion" over four years.
A company spokeswoman was unable to confirm a newspaper report that it may have improperly booked more than $6 billion in revenues.
A previous estimate had suggested a miscalculation of $3 billion for the 1997 to 2000 period.
The revelations follow a US Securities and Exchange Commission investigation of Xerox's accounting methods for sales and revenues begun in April.
According to the Wall Street Journal, the SEC in April estimated that Xerox had improperly accounted for $3 billion in revenues for the years from 1997 to 2000.
The latest edition of the paper says the audit also looked at the year 2001 and found fresh accounting problems.
Despite the rebuttals, the claims of yet another accounting scandal have hit Xerox's share price on Wall Street.
In pre-market trading Xerox it was down by between 25 per cent and 30 per cent.