Short-term rentals are allowed in Contra Costa County, including within the unincorporated areas around Martinez, subject to the County’s STR ordinance (Ordinance 2020‑12). The City of Martinez does not publish its own STR regulations; unincorporated areas are governed by the County’s ordinance, which the Board of Supervisors approved to manage hosted and non‑hosted STRs. You must secure county approvals (permit, business license, transient occupancy registration) before listing or renting.

How to start an STR business in this market (Contra Costa County)

1. Confirm zoning and location

• Only unincorporated Contra Costa County is governed by the County STR ordinance. If your property is within Martinez city limits, the County does not regulate city‑specific STRs. To determine status, contact the County Planning Department or use the County’s Property/Zoning Lookup tool.

2. Verify you can operate an STR under County rules

• Units must be in permitted residential districts (single‑family, multi‑family, planned unit, agriculture not under Williamson Act) and cannot be accessory dwelling units (ADUs).
• Hosted rentals are capped at 180 days/year; non‑hosted at 90 days/year; absolute cap is 180 days/year.
• If your plans deviate from standards (e.g., exceed day limits), apply for a discretionary land‑use permit.

3. Apply for the County STR permit (ministerial)

• Complete the Short‑Term Rental Checklist and Application and submit via email to the Planning Division (see Contact).
• A planner will assign your case, request fees, and issue the permit if compliant.
• Neighbors within 300 feet receive notice and the responsible party contact and Code Enforcement information.

4. Obtain required business approvals before renting

• Business License from the relevant city/agency (see City and Agency Contacts directory).
• Transient Occupancy Registration Certificate from the County Tax Collector’s Office before renting or offering to rent.
• Provide a copy of the business license to the County (see Permit Renewal/Enforcement below).

5. Comply with operational rules at all times

• Maintain responsible party contact details, adhere to occupancy/gathering limits, avoid signage and special events, and preserve residential traffic/noise standards.

Required documents, permits, licenses, and guidelines

County STR Permit (required)

• STR Application (full, accurate submittal).
• Planners review for compliance; permit is ministerial if standards are met.
• Renewal required annually; file renewal at least 30 days before expiration.

Business License

• Required before renting or offering to rent. Contact the appropriate city/agency using the County’s City and Agency Contacts directory.

Transient Occupancy Registration Certificate (TOT)

• Required before renting or offering to rent; obtained through the County Tax Collector’s Office.
• State law presumes collection by platforms; local tax collection is handled by the County Tax Collector.

Operation Standards (adherence is mandatory)

• Day caps: non‑hosted ≤ 90 days/year; hosted ≤ 180 days/year; overall ≤ 180 days/year.
• Occupancy: ≤ 2 guests per bedroom + 2 additional; children under 12 not counted.
• Parking: ≤ 3 bedrooms → ≥ 1 off‑street space; ≥ 4 bedrooms → ≥ 2 off‑street spaces.
• gatherings: ≤ 20 total persons on site.
• No special events (conferences, weddings, commercial events).
• No signage.
• No excessive traffic or noise inconsistent with residential use.
• No obstruction of roads.
• No use of ADUs as STRs.

Discretionary Permit (if standards cannot be met)

• Available via land‑use permit to deviate from day caps, parking minimums, or guest limits.
• Processed as a discretionary permit with noticing and public hearing if requested.
• No deviations allowed to operational standards.

Specific regulations (City, County, State)

City of Martinez

• City‑specific STR rules were not provided; the city appears to rely on the County’s ordinance for unincorporated areas. If your property is inside city limits, consult the City for any municipal STR requirements or local taxes.

Contra Costa County (unincorporated areas, Ordinance 2020‑12)

• Definitions and day caps: hosted ≤ 180 days/year; non‑hosted ≤ 90 days/year; overall ≤ 180 days/year.
• One STR per lot; no STRs in buildings with 5+ dwelling units.
• Occupancy, parking, gathering caps as above.
• ADUs prohibited as STRs.
• Responsible party must be ≥ 18 years old and live within 30 miles, available by phone during rentals to respond to complaints or enforcement concerns.
• 300‑foot neighbor notice with responsible party and Code Enforcement contact upon permit issuance.
• No deviations to operational standards (traffic, noise, obstructions, gatherings, events, signage).

California (state‑level guidance, unincorporated Contra Costa)

• Transient Occupancy Tax (TOT): Hosts operating in unincorporated County areas collect and remit TOT to the County Tax Collector (platforms often collect on hosts’ behalf). Failure to comply can result in penalties and interest.
• Insurance: Many hosts carry short‑term rental insurance to cover liability and property risks given the higher turnover and guest variability.
• Registration/Disclosure: The state does not impose a statewide STR permit; local ordinances govern. If you conduct business under a fictitious business name, register with the appropriate county or state agency.
• AB 1129 (2023) requires certain short‑term rental platforms to verify local compliance (e.g., permit number) and remit TOT.
• Safety best practices (often required by platforms): operational smoke and carbon monoxide detectors, posted emergency egress, local emergency contacts, and clear house rules.

Contact information (local authority in charge of STRs)

County Departments & Permits

• Planning & Building (Building and Planning): 925‑655‑2700
• Public Works (encroachment permits): 925‑313‑2000
• Application and Permit Center (Planning) — ePermits and Planning questions: see Planning Staff email (under Getting Help)
• ePermits Center Technical Support: for application portal issues
• Code Enforcement: see County Code Enforcement Division

Application Submittal

• Submit STR application and required documents via the Planning Division email listed under “Getting Help.”

Business Licensing

• Contact the appropriate city or agency using the County’s City and Agency Contacts directory (Business License requirements vary by jurisdiction).

Taxation

• County Tax Collector’s Office (Transient Occupancy Registration Certificate/TOT): obtain local certificate, remit TOT, and confirm platform remittance status.
• For Tax Collector contacts, use the County’s City and Agency Contacts directory.

Links to source pages (if available)

• County STR Portal (Permitting Process, Standards, Getting Help): www.contracosta.ca.gov/10303/Short-Term-Rentals
• STR Ordinance Summary (Ordinance 2020‑12): www.contracosta.ca.gov/DocumentCenter/View/67827/STR_Summary
• Short‑Term Rental Application (PDF): www.contracosta.ca.gov/DocumentCenter/View/68142/Short-Term-Rental-Application-Fillable-PDF
• City and Agency Contacts (Business Licenses): www.contracosta.ca.gov/9984/City-and-Agency-Contacts
• County STR Ordinance (Municode): library.municode.com/ca/contra_costa_county/codes/ordinance_code?nodeId=TIT8ZO_DIV88SPLAUS_CH88-32SHRMRE

Notes for investors

• Verify zoning and permit eligibility before acquiring or investing in a property. The County requires a valid STR permit and a business license prior to operating.
• Monitor compliance year‑round: TOT remittance, responsible‑party availability, occupancy and gathering caps, parking and noise rules, and the prohibition on events and signage.
• If you need flexibility beyond the standards (e.g., more than 90 non‑hosted days), prepare to pursue a discretionary land‑use permit with the added time and risk of a public hearing.
• For properties within Martinez city limits, seek city‑level licensing or tax requirements and any local rules, as the County ordinance applies only in unincorporated areas.