From the IRS
The Worker, Homeownership, and Business Assistance Act of 2009, P.L. 111-92, was enacted in November 2009. Among its provisions, the act mandates e-filing by almost all return preparers; it requires any return preparer who files more than 10 individual income tax returns per year to e-file those returns, starting in 2011.
Recently, the Electronic Tax Administration Advisory Committee recommended in its annual report to Congress that the mandate be phased in over three years and be applied only to preparers who file Forms 1040, U.S. Individual Income Tax Return.
The IRS has not adopted this recommendation, but it has announced that it will phase the requirement in over two years. Starting January 1, 2011, tax return preparers who anticipate filing 100 or more federal individual or trust tax returns will be required to e-file those returns. Then, starting January 1, 2012, the e-filing requirement will apply to preparers who anticipate filing more than 10 individual or trust tax returns.