A nonprofit organization is required to register with the PDC as an incidental committee if it has the expectation of spending or spends $25,000 or more in a calendar year on one or more election campaigns or political committees (including a sponsored or affiliated committee), and is receiving payments that in aggregate total $10,000 or more from a single source. RCW 42.17A.207
A “nonprofit” for purposes of the incidental committee law is one of the following: 
  1. Eligible for an exemption under section 501(c) of the federal Internal Revenue Code
  2. An organization, association or corporation whose income is not paid directly or indirectly to members, stockholders or leaders; or
  3. A limited partnership or limited liability company whose general partner or managing member is an entity described in 1 or 2. WAC 390-05-535

Any organization that is only remitting payments in an aggregated form – such as a nonprofit that processes campaign donations solicited by candidates or political committees – is not required to register as an incidental committee. RCW 42.17A.005(25)

A nonprofit whose only activity is independent expenditures – defined as expenditures that are made in support of or opposition to a candidate but without the candidate's or ballot measure committee’s cooperation, consultation or collaboration – may still need to register as an incidental committee in addition to filing a C-6 report.