The Internal Revenue Service said even though they have no electronic filing requirement, more than 780,000 small businesses have opted to e-file their tax returns this year, up more than 50 percent from last year.

Many large corporations are voluntarily e-filing as well. The more than 42,000 large corporations that e-filed far exceeded the approximately 22,000 that were required to file by the Sept. 17 deadline, said the IRS.

Starting in 2006, certain corporations with assets of more than $50 million were required to file their Form 1120 and 1120-S electronically. Approximately 15,500 of these corporations filed their returns electronically last year. Starting in 2007, certain corporations with assets of more than $10 million were required to file electronically.

"Corporations of all sizes are seeing the long range advantages of integrating their tax filing in an electronic environment along with their tax and financial accounting," said IRS Treaty Administration Director Elvin Hedgpeth, who led the implementation of e-filing for large corporations. "While large and mid-size corporations are required to e-file, many small corporations are seeing the advantages of e-filing voluntarily."