In order to do business under a fictitious name in Contra Costa County, you must do two things:
(1) Publish a notice that you are doing business under the fictitious name. The notice must appear in a general circulation newspaper once a week for four successive weeks. The newspaper must be circulated in the county where you are doing business.
(2) File an affidavit with the county clerk proving that you have met the publishing requirement.
These requirements are the same as those established by the State of California. They are outlined in the Business and Professions Code. The exact legal wording follows.
Section 19917 (the publishing requirement):
(a) Within 30 days after a fictitious business name statement has been filed pursuant to this chapter, the registrant shall cause a statement in the form prescribed by subdivision (a) of Section 17913 to be published pursuant to Section 6064 of the Government Code in a newspaper of general circulation in the county where the fictitious business name statement was filed or, if there is no such newspaper in that county, in a newspaper of general circulation in an adjoining county. If the registrant does not have a place of business in this state, the notice shall be published in a newspaper of general circulation in Sacramento County.
(b) Subject to the requirements of subdivision (a), the newspaper selected for the publication of the statement should be one that circulates in the area where the business is to be conducted.
(c) If a refiling is required because the prior statement has expired, the refiling need not be published unless there has been a change in the information required in the expired statement, provided the refiling is filed within 40 days of the date the statement expired.
(d) An affidavit showing the publication of the statement shall be filed with the county clerk where the fictitious business name statement was filed within 30 days after the completion of the publication.
Section 17924 (the affidavit filing requirement):
(a) The county clerk shall furnish without charge a form satisfying the requirements of subdivision (a) of Section 17913. The form prepared by the county clerk, or the material provided by him with the form, shall include statements substantially as follows:
(1) "Your fictitious business name statement must be published in a newspaper once a week for four successive weeks and an affidavit of publication filed with the county clerk when publication has been accomplished. The statement should be published in a newspaper of general circulation in the county where the principal place of business is located. The statement should be published in such county in a newspaper that circulates in the area where the business is to be conducted (Business and Professions Code Section 17917)."