Two campaign committees in the state will pay $15 million. The fine is equal to the amount the committees received, which officials said was improperly reported.
Two non-profits, one of which is linked to billionaires Charles and David Koch, were also ordered to pay $1 million.
The donations helped to derail Gov. Jerry Brown's tax hike, and supported a measure intended to limit unions' political power.
The fines came after a yearlong investigation, the Los Angeles Times reported.
Anonymous donations have increased dramatically since 2010 when the Supreme Court ruled non-profits can spend an unlimited amount of money on elections.
Rich donors then began using the non-profits as middle men, the Times said.
The non-profits are not required to disclose their donors, but the investigation uncovered some identities.
Charles Schwab gave $6.4 million and the Fisher family, owner of Gap Inc., donated more than $9 million.
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