Up to now only section 501(c)(3) public charities with assets totally $10 million or more and those filing Form 990-N were required to file electronic Form 990s. With the Taxpayer First Act, all 501(c)(3) public charities will be required to file their Form 990, Form 990EZ or Form 990N electronically. This requirement will be phased in over the next couple of years.
Article - Mandatory Electronic Filing of Form 990s