If your business will be using a fictitious name, then within 40 days of the business start date you will need to file a Fictitious Business Name Statement.
Sonoma County Clerk-Recorder-Assessor
Fictitious Business Name
2300 County Center Drive, Suite B-177
Santa Rosa, CA 95403
$40 fee plus $9 for each additional owner/business name, (plus cost of publishing statement in adjudicated newspaper). (If no changes, good for 5 years.) (As of June 2016 - for current info see Fictitious Business Name Information.)
Statement must be published once a week for four consecutive weeks in an adjudicated Sonoma County newspaper (first publication must begin within 30 days of when statement was filed).