
1065
The IRS has mandated that all 1065 partnerships with 100 or more K1s must be filed electronically. A penalty of $50 per partner will be assessed for those not complying with the mandate. Certain waivers are available, but are very limited. See IRS Publication 1524 for additional details.
1120/1120S
The IRS has mandated that all 1120/1120S corporations with assets of $10 million or more and filing 250 federal returns must e-file.
990
The IRS has mandated that all 990 exempt organizations with assets of $10 million or preparers filing 250 federal returns must e-file. 990PF has been added to the 250 federal return mandate for tax year 2006. See IRS Publication 4206 for additional details.
If you fall into any of the mandates and do not currently e-file, you are required to apply with the IRS to obtain an EFIN. Complete the application at http://www.irs.gov/pub/irs-pdf/f8633.pdf or use IRS e-services to fill out the application online.