The Boat Ownership and Location Change Form (BOAT-12 SMCA-339) is a letter from the San Mateo County Assessor-County Clerk-Recorder that boat owners complete when a boat on the Assessor's records was sold, moved out of the county or destroyed. It is one of the forms in the San Mateo County property tax process for boats: the Assessor values the boat and the Tax Collector collects the resulting bill. On this page you can fill out the form online on FillingPDF and download or print the completed PDF; the original is published by the Assessor's office at smcacre.gov.
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What is BOAT-12 SMCA-339?
The Boat Ownership and Location Change Form is a letter the San Mateo County Assessor-County Clerk-Recorder sends to boat owners, who complete it to report that a boat was sold, moved out of the county or destroyed.
The letter opens by telling the owner that Assessor's Office records show them as the owner of a boat as of January 1, 2026. The Assessor is responsible for valuing all assessable property in the County, and the Tax Collector collects the resulting tax bill. The form lets you correct the record when the boat is no longer yours or no longer in the county.
It has three sections, and you complete the one that applies:
- 1. Boat Sold Prior to January 1, 2026, which asks for the new owner's details, the sale date and the sales price.
- 2. Boat Moved Out of San Mateo County Prior to January 1, 2026, which asks for the new location and the date moved.
- 3. Boat Destroyed, which asks for the date and place.
Each section asks whether the Department of Motor Vehicles (DMV) was notified. The form states that failing to notify the DMV will delay the cancellation of your tax bill. It ends with a certification under penalty of perjury and is identified on the page as BOAT-12 SMCA-339. It reports a change; it does not itself cancel a bill.
Who needs to file BOAT-12 SMCA-339?
Owners of a boat that the San Mateo County Assessor's Office shows as owned by them as of January 1, 2026 complete this form when one of three things is true:
- You sold the boat before January 1, 2026 (Section 1).
- You moved the boat out of San Mateo County before January 1, 2026 (Section 2).
- The boat has been destroyed (Section 3).
The form tells you to complete in full the section that applies, and to return the signed letter if any section is completed. It does not ask boat owners whose situation is unchanged to return it.
Keep the form's own warning in mind: the owner of record on January 1 owes taxes for the entire fiscal year, and the county where the boat is located on January 1 is the county owed taxes for that fiscal year. A sale or move after that date is therefore not what Sections 1 and 2 describe.
For a destroyed boat, the form directs you to contact the Assessor Division about a calamity loss; the dollar threshold is printed on the form. The form does not describe who else may sign for an owner, so contact the Assessor's office if someone other than the owner of record must respond.
When to file BOAT-12 SMCA-339
Return the form immediately if you complete any of its sections: the letter says to return the signed letter "immediately." It sets no calendar due date of its own.
The dates that matter are the ones the form asks you to report. Sections 1 and 2 cover a sale or a move that happened prior to January 1, 2026, because the owner of record on January 1 owes taxes for the entire fiscal year and the county of location on January 1 is the county owed taxes for that year.
The form also states DMV notification deadlines that run separately from this letter:
- A seller must notify the DMV within five (5) days from the date of sale (Section 9911 of the Vehicle Code).
- The DMV should be notified of any address or owner change within fifteen (15) days (Section 9865 Vehicle Code).
- For a destroyed boat, the DMV should be notified within fifteen (15) days (Section 9864 Vehicle Code).
The form says that failing to notify the DMV will delay the cancellation of your tax bill.
How to fill out BOAT-12 SMCA-339
Identify the boat
At the top, enter the VESSEL ID and the ACCOUNT NUMBER shown for your boat. Then decide which of the three sections applies: sold, moved out of the county, or destroyed.
Complete Section 1 if the boat was sold
For a sale before January 1, 2026, complete all lines: name of new owner, address, city, ZIP, date sold and sales price. Mark YES or NO for whether the DMV was notified and enter when the slip was vacated.
Complete Section 2 if the boat moved
For a move out of San Mateo County before January 1, 2026, enter the new location, county and date moved. Mark YES or NO for DMV notification and enter when the slip was vacated.
Complete Section 3 if the boat was destroyed
Enter the date destroyed and where, and mark YES or NO for DMV notification. The form tells you to contact the Assessor Division about a calamity loss.
Add any detailed explanation
If you need more room, continue on the backside of the letter, as the form instructs. Keep the explanation tied to the section you completed.
Sign the certification
Enter the date and your signature, your printed name and a telephone number where you can be reached from 8:00 a.m. to 5:00 p.m. The certification is made under penalty of perjury.
Review and download the completed PDF
Check that only the applicable section is completed and that it is complete in full. Download or print the completed PDF from FillingPDF and return it to the Marine Section address described under How to submit.
How to submit BOAT-12 SMCA-339
The form is a letter that you sign and return to the Assessor's office by sending it to the address printed on it.
- Return address: Mark Church, Assessor-County Clerk-Recorder, Marine Section, 555 County Center, Redwood City, CA 94063-1639.
- Contact details printed on the form: telephone (650) 363-4501, fax (650) 599-7456, email [email protected] and web www.smcacre.gov. The form lists these as the office's contact details and names no channel other than returning the signed letter to the address above.
Before you return it, complete the section that applies in full, sign and date the certification, print your name and add a daytime telephone number (the form asks for 8:00 a.m. to 5:00 p.m.). Use the back of the letter for any detailed explanation, as the form directs. Notify the DMV separately; the form says the DMV must be notified and that failing to do so delays cancellation of your tax bill. FillingPDF lets you fill out and download the PDF; submission follows the channels above.
Common mistakes to avoid
- Leaving the applicable section partly blank; the form says to complete it IN FULL, including Vessel ID and Account Number.
- Not notifying the DMV and assuming the Assessor will cancel the tax bill anyway; the form says failure to notify the DMV delays cancellation.
- Reporting a sale or move that happened after January 1, 2026 as if it removed the tax; the owner of record on January 1 owes taxes for the entire fiscal year.
- Waiting to return the letter; it asks that a completed, signed letter be returned immediately.
- Returning the form unsigned or without the date and printed name required by the certification under penalty of perjury.
- Completing Section 3 for a destroyed boat without contacting the Assessor Division about a calamity loss, as the form directs.
- Omitting the new owner's name, address, date sold or sales price in Section 1, which asks you to complete all lines.
- Squeezing a long explanation into the front when the form says to continue on the backside for any detailed explanation.
Frequently asked questions
What is the San Mateo County Boat Ownership and Location Change Form?
It is a letter from the San Mateo County Assessor-County Clerk-Recorder (form BOAT-12 SMCA-339) that boat owners complete to report a boat sold, moved out of the county or destroyed. The Assessor values boats; the Tax Collector collects the resulting tax bill.
Who has to return the BOAT-12 form?
Owners shown on the Assessor's records as owning a boat as of January 1, 2026 whose boat was sold, moved out of San Mateo County or destroyed. The form says to complete the applicable section in full and return the signed letter if any section is completed.
Do I still owe tax if I sold my boat after January 1?
Yes, according to the form: the owner of record on January 1 owes taxes for the entire fiscal year. Section 1 applies to a boat sold prior to January 1, 2026, and Section 2 to a boat moved out of the county before that date.
Do I have to notify the DMV when I sell or move my boat?
Yes. The form says the seller must notify the DMV within five days of sale (Vehicle Code Section 9911), and that address or owner changes should be reported within fifteen days (Section 9865). Failing to notify the DMV delays cancellation of your tax bill.
Where do I send the completed boat form?
Return the signed letter to Mark Church, Assessor-County Clerk-Recorder, Marine Section, 555 County Center, Redwood City, CA 94063-1639. The form also lists the office phone (650) 363-4501 and email [email protected] for questions.
What do I do if my boat was destroyed?
Complete Section 3 with the date destroyed and where, and say whether the DMV was notified within fifteen days (Section 9864 Vehicle Code). The form also tells you to contact the Assessor Division about a calamity loss.
Which county is owed property tax on a boat?
The county where the boat is located on January 1 is owed taxes for that fiscal year, the form says. That is why Section 2 asks about boats moved out of San Mateo County prior to January 1, 2026.
Can I fill out Form BOAT-12 online on FillingPDF?
You can complete the PDF online on FillingPDF and download or print it. FillingPDF is an independent service, is not affiliated with the Assessor's office and does not file the form; you return it to the Marine Section yourself.
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