The San Carlos sales tax rate is 9.375% in 2026, combining California’s 7.25% statewide base with 2.125% in voter-approved district taxes collected in San Mateo County. Retailers add it at checkout on most tangible goods sold inside the city, from electronics and furniture to clothing and auto parts.1California Department of Tax and Fee Administration. California City and County Sales and Use Tax Rates
Because district taxes are voter-approved and often carry sunset dates, the combined rate can move. San Mateo County’s half-cent Measure K, for example, runs through March 31, 2043. The CDTFA’s rate lookup tool is the quickest way to confirm the current figure for a specific San Carlos address before you file or quote a price.
How the 9.375% Rate Is Built
The 7.25% statewide base is set by California law and applies everywhere in the state. It funds the state General Fund, local public safety, health and social services realignment, and a local share split between county transportation and city or county operations.2California Department of Tax and Fee Administration. Detailed Description of the Sales and Use Tax Rate
On top of that base, San Carlos collects 2.125% in district taxes. These are local and countywide measures passed by voters under Revenue and Taxation Code Section 7285.9, which lets a California city levy a transactions and use tax in 0.125% increments with majority approval. San Mateo County’s Measure K sits inside that district layer.
What’s Taxable and What Isn’t
Sales tax applies to most tangible personal property. Several categories are not taxed, and the lines matter for both shoppers and small businesses.
Groceries bought for home consumption are exempt under Revenue and Taxation Code Section 6359. Fresh produce, dairy, bread, and most unprepared food items qualify.3California Department of Tax and Fee Administration. Sales and Use Tax Regulations – Article 8 The line gets drawn at prepared food: hot meals, heated sandwiches, and food sold for immediate consumption at a restaurant or deli counter are taxable. Carbonated beverages, alcohol, and candy are also taxable regardless of where you eat them.
Prescription medicine is exempt under Section 6369, as is most medical equipment sold by prescription.
Businesses in manufacturing, research and development, or electric power generation may claim a partial exemption on qualifying equipment under Revenue and Taxation Code Section 6377.1. That exemption is in effect through June 30, 2030.4California Department of Tax and Fee Administration. Tax Guide for Manufacturing, and Research and Development, and Electric Power Equipment and Buildings Exemption
Use Tax on Out-of-State and Online Purchases
When you buy something from an out-of-state retailer that doesn’t collect California sales tax, you owe use tax at the same 9.375% rate. If the item would have been taxed had you bought it in San Carlos, the state expects the equivalent from you.
Most large online retailers already collect because they exceed California’s $500,000 economic nexus threshold. Smaller sellers, private-party purchases, and items picked up while traveling can slip through, and in those cases the buyer is responsible for reporting and paying.5California Department of Tax and Fee Administration. California Use Tax For Personal Use
You have two ways to pay personal use tax. The simplest is reporting it on your California state income tax return (Form 540 or 540 2EZ). For nonbusiness purchases under $1,000, the CDTFA’s Use Tax Lookup Table lets you estimate without tracking individual receipts. The other option is paying the CDTFA directly through its online portal by filing a one-time use tax return.
One exception: vehicles, vessels, aircraft, and mobile homes must be reported directly to the CDTFA rather than on your income tax return. The same applies to cigarettes and tobacco products.
Seller’s Permit and Economic Nexus
Any business selling or leasing tangible personal property in San Carlos needs a California seller’s permit before its first sale. The CDTFA issues the permit at no charge through its online registration system.6CA.gov. Apply for a Sellers Permit The application asks for personal identification, bank account information, estimated sales volume, and the type of products you plan to sell. If you bought an existing business, you’ll also need the previous owner’s name and permit number.7California Department of Tax and Fee Administration. Do You Need a California Sellers Permit (Publication 107)
Out-of-state retailers shipping into San Carlos trigger California’s economic nexus rules if they exceed $500,000 in total gross sales (including marketplace sales) during the current or previous calendar year. Once that threshold is crossed, the seller must register with the CDTFA and begin collecting California sales tax.8California Department of Tax and Fee Administration. Use Tax Collection Requirements Based on Sales into California California uses a dollar-volume test with no separate transaction count threshold.
Filing Returns and Deadlines
Sales tax returns go through the CDTFA’s online portal, which walks you through total sales, taxable sales, and deductions before calculating what you owe.9California Department of Tax and Fee Administration. Online Services – File a Return The CDTFA assigns each business a filing frequency based on sales volume. Most businesses file monthly, quarterly, or annually. Quarterly deadlines are:10California Department of Tax and Fee Administration. Filing Dates for Sales and Use Tax Returns
- January through March: due April 30
- April through June: due July 31
- July through September: due October 31
- October through December: due January 31
Monthly filers owe their return by the last day of the following month. Higher-volume businesses on quarterly prepayment schedules must also submit prepayments by the 24th of the month following each prepayment period. When a due date falls on a weekend or state holiday, the deadline moves to the next business day. Electronic funds transfer payments must clear before 3:00 p.m. Pacific time on the due date to count as timely.
The CDTFA accepts direct bank withdrawals at no charge, credit cards (with a 2.3% processing fee from the card vendor), electronic funds transfer, and mailed checks or money orders.11California Department of Tax and Fee Administration. Online Services – Make a Payment Businesses required to pay by EFT who use a different method face an additional penalty, so confirm your assigned payment method when you receive your permit.
Late Filing: Penalties and Interest
Missing a filing deadline or paying late triggers a 10% penalty on the unpaid tax. Filing a late return also carries a separate 10% penalty on the tax due for that period. If you are both late filing and late paying, the combined penalty is capped at 10% rather than stacking to 20%.12California Department of Tax and Fee Administration. Interest, Penalties, and Collection Cost Recovery Fee (Publication 75)
Interest accrues on top. For 2026, the CDTFA charges 10% annually on unpaid balances, applied at a monthly factor of 0.00833 for each month or partial month overdue.13California Department of Tax and Fee Administration. Interest Rates Unlike the penalty, interest cannot be waived unless the delay was caused by a CDTFA employee’s error.
Requesting Penalty Relief
If you missed a deadline for reasons genuinely beyond your control, the CDTFA may waive the penalty. You can request relief online through your CDTFA account or by submitting Form CDTFA-735. The standard is “reasonable cause and circumstances beyond your control,” which generally means something like a medical emergency, natural disaster, or death in the family rather than simple forgetfulness.14California Department of Tax and Fee Administration. Request Relief
The CDTFA typically won’t process a relief request until the full tax amount is paid, and interest still applies even if the penalty is waived. You can also request a one-month filing extension before the deadline passes, which can keep penalties from being assessed in the first place.
A Possible Rate Change in November 2026
The San Carlos City Council is considering a half-cent sales tax measure for the November 2026 ballot. If voters approve it, the measure would generate an estimated $6 million a year for city services and raise the total San Carlos rate by 0.50%, bringing it to 9.875%.15City of San Carlos. Potential November 2026 Revenue Measure Residents and business owners should watch for confirmation that the measure qualifies for the ballot and, if it passes, the effective date for the new rate.