TaxAct supports Form 990, Return of Organization Exempt from Income Tax.
Generally, tax-exempt organizations must file an annual informational return. Tax-exempt organizations that have annual gross receipts not normally in excess of $25,000 are not required to file the annual information return. In addition, churches and certain religious organizations, certain state and local instrumentalities, and other organizations are excepted from the annual return filing requirement.
IRS Publication 557 Tax Exempt Status for Your Organization
For an explanation of the filing and recordkeeping rules that apply to section 501(c)(3) organizations:
Compliance Guide for 501(c)(3) Public Charities
Compliance Guide for 501(c)(3) Private Foundations
For additional information regarding Form 990 e-file rejections, contact the IRS Help Desk at (866) 255-0654.