If a copy of the summons and of the complaint cannot with reasonable diligence be personally delivered to the person to be served, a summons may be served by leaving a copy of the summons and of the complaint at such person’s dwelling house, usual place of abode, usual place of business, or usual mailing address other than a United States Postal Service post office box, in the presence of a competent member of the household or a person apparently in charge of his or her office, place of business, or usual mailing address other than a United States Postal Service post office box, at least 18 years of age, who shall be informed of the content thereof, and by thereafter mailing a copy of the summons and of the complaint (by first-class mail, postage prepaid) to the person to be served at the place where a copy of the summons and of the complaint were left. Service of a summons in this manner is deemed complete on the 10th day after the mailing. (CCP 415.20(b))
Judicial Council Comment: “Personal delivery must be attempted in all cases where this alternative (substitute) method of service is used.”
The term “usual place of business” includes a defendant’s customary place of employment as well as his own business enterprise.