San Mateo County, CA Short-Term Rentals: Night Caps (2026)

San Mateo County limits how often a Coastal Zone short-term rental can operate. Zoning Regulations Section 6401.3(2)(c) states that a short-term rental cannot be rented for more than one hundred eighty (180) nights per calendar year. The ordinance creates a meaningful exception: any night during which the short-term rental is rented while the property owner is present at the address where the STR is located does not count against the 180-night limit. In practice, this means an absentee/whole-home operator is held to 180 rented nights, while an owner who shares the home during stays can exceed that number because owner-present nights are excluded from the count. The cap is enforced through the County's recordkeeping requirement: under Section 6401.3(6)(l), each owner must keep true and accurate records of the number of nights the unit is rented and the amounts paid, retain them for at least three years, and produce them within 10 calendar days' notice to the Department, Tax Collector, or Auditor. The 180-night limit operates alongside the permit's three-year term (Section 6401.3(2)(e)) and the County's broader interest in preserving rental housing stock and neighborhood character in the coastal communities. There is no separate weekly or monthly cap in the ordinance beyond the annual 180-night ceiling and the under-30-consecutive-day definition that distinguishes short-term from long-term tenancy.