California substitute service (CCP §415.20)

Substitute service is California’s fallback when a defendant can’t be reached for personal service. The rules live in California Code of Civil Procedure §415.20. Used correctly, it is just as valid as personal service. Used incorrectly, the court will quash service and you start over.

Short answer

After three diligent attempts at personal service at different times of day, the server can leave the papers with a "competent member of the household 18 years or older" at the defendant’s residence (or with an authorized person at place of business), then mail a copy to the same address. Service is complete 10 days after mailing.

When it matters

• Default judgment requires personal service OR proper substituted service
• Substitute service mistakes are the most common reason CA courts set aside default judgments
• If the defendant later moves to quash service, the GPS-stamped attempt log + a properly executed POS-040 is your defense

The diligence requirement

CCP §415.20 does not specify a number. CA courts have held that three attempts at different times (morning / afternoon / evening, with at least one weekend attempt) is the floor. Some judges expect 4-5 for residential, especially if the defendant is known to work irregular hours.

Each attempt must:

• Be GPS-stamped to verify location
• Note time, who answered (or didn’t), and any observations
• Be reasonably spaced (not three knocks in 10 minutes)

The leave-and-mail step

Once diligence is met:

1. Leave with a competent adult at the dwelling. A teenager is not enough; the recipient must be 18+. The CCP says "apparently in charge" — in practice the server identifies themselves and confirms the person lives there.
2. Mail a copy to the same address by first-class mail, postage prepaid. The mailing is mandatory; without it the service fails.
3. Wait 10 days. Service is deemed complete 10 days after the mailing under CCP §415.20(b). All response deadlines run from that date.

The POS-040 sub-service declaration

The Judicial Council POS-040 form has a specific section for substituted service. The server fills in:

• Who they left papers with (name + age + relationship)
• Date and time of leaving
• Date the mailed copy was sent
• Address where the mailed copy was sent

Skip any field and the court clerk may reject the POS as defective. Servd’s AI drafts the language; a human reviewer + the licensed server sign before filing.

Common mistakes

• Two attempts then sub-service. CCP says "after reasonable diligence"; courts have held two is rarely enough.
• Three attempts all in the morning. Diligence requires varied times of day.
• Sub-service on a minor. Recipient must be 18+. A 17-year-old roommate doesn’t qualify.
• Forgetting to mail. Without the mailed copy the service is incomplete; the 10-day clock never starts.
• Wrong address. Sub-service at the defendant’s workplace requires "the person apparently in charge" (CCP §415.20(b)(2)); not just any coworker.

What Servd does

GPS-stamped attempts in your /me/cases timeline. AI computes when diligence has been met and surfaces the sub-service option to the field server. Human reviewer checks the POS-040 sub-service declaration is complete and the mail-back date is recorded. CCP §415.20 specifics auto-cited.

Related guides

• [California proof of service](/guides/california-proof-of-service)
• [What is process serving?](/guides/what-is-process-serving)
• [What if a defendant avoids service?](/guides/defendant-avoids-service)

This is not legal advice; consult an attorney about your case.