Generally, an exempt organization must file Form 109 if its unrelated trade or business income is more than $1,000. Unrelated business income is income from a trade or business, regularly carried on, which is unrelated to the organization's exempt purpose.
However, homeowners' associations and Mutual Water Companies exempt under California Revenue & Taxation Code section 23701t and political organizations exempt under California Revenue & Taxation Code section 23701r must file Form 100 if their gross taxable income from nonexempt-function sources is more than $100.
For more information, see the following publications and forms:
Pub. 1028 - Guidelines for Homeowners' Association
Pub. 1075 - Exempt Organization - Guide for Political Organizations
Form 100 - California Corporation Franchise or Income Tax Return
Form 109 - California Exempt Organization Business Income Tax