3 county-level rules, plus city-specific rules for 1 city in San Mateo County, California.
Verified from official government sources
Unincorporated San Mateo County does not require a permit for occasional residential garage/yard sales. Sales are treated as incidental residential activity, not commercial operations, so long as they remain occasional and comply with County Code frequency and sign rules. Merchandise must be personal property, not goods purchased for resale — the latter would require a business license and zoning clearance as a home business or retail operation.
Unincorporated San Mateo County does not codify a specific numeric annual cap on garage sales per household, but treats sales as permissible incidental residential use when occasional — typically understood as 2-4 per year. Holding sales with greater frequency or for extended durations can trigger home-business zoning review, require a business license, and constitute an unpermitted retail use of residential property. HOA communities often impose stricter limits (commonly 1-2 per year).
Unincorporated San Mateo County garage sales must stay within reasonable daylight hours, typically 8 AM to 6 PM, and remain within the Chapter 4.88 Noise Control exterior limits at the property line. Friday-Sunday weekend sales are most common. All merchandise, tables, and signs must be removed from public view at the end of each sale day. Leaving items outside overnight can trigger property blight/nuisance enforcement.
1 cities in San Mateo County have their own garage & yard sales rules. Each link goes to that city's dedicated page with code citations.
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