Avoid Penalties by Understanding Postmarks

Property tax payments must be received or postmarked by the delinquency date to avoid penalties. If a payment is received after the delinquency date, with no postmark, the payment is considered late and penalties will be imposed, in accordance with State law. A penalty of ten percent (10%) of the tax amount due on the first installment and a penalty of ten percent(10%) of the tax amount due on the second installment and a $40.00 cost will be imposed. For example, if the amount due for the 1st installment is $2,000, a 10% penalty of $200 will be imposed. If the amount due for the 2nd installment is $2,000, a 10% penalty of $200 and a $40 cost (total $240) will be imposed.

POSTMARKS are imprints on letters, flats, and parcels that show the name of the United States Postal Service (USPS) office that accepted custody of the mail, along with the state, the zip code, and the date of mailing. The postmark is generally applied, either by machine or by hand, with cancellation bars to indicate that the postage cannot be reused.

Taxpayers who send their payments by mail are cautioned that the USPS only postmarks certain mail depending on the type of postage used, and may not postmark mail on the same day deposited by a taxpayer.

Postage that is postmarked:

STANDARD POSTAGE STAMPS: Stamps purchased and affixed to mail as evidence of the payment of postage.

Postage that is not postmarked:

  • METERED MAIL: Mail on which postage is printed directly on an envelope or label by a postage machine licensed by the USPS. Many private companies use these types of postage machines.
  • PRE-CANCELLED STAMP: Stamps sold through a private vendor, such as stamps.com®.
  • AUTOMATED POSTAL CENTER (APC) STAMPS: Stamps, with or without a date, purchased from machines located within a USPS lobby.
  • PERMIT IMPRINT: Pre-sorted mail used by bill pay services, such as online home banking.

If you use these types of postage, the USPS will not postmark your mail. You will be charged a 10% penalty and a $40 cost, if applicable, if we do not receive your mailed payment by the delinquency date.

Other options:

Purchase and complete a CERTIFICATE OF MAILING: from the USPS, which is a receipt that provides evidence of the date that your mail was presented to the USPS for mailing. It can only be purchased at the time of mailing through the USPS. The USPS charges a fee for this service.

Purchase a POSTAGE VALIDATED IMPRINT (PVI) Label: from a USPS retail counter or window. The PVI is applied to a piece of mail by personnel at the retail counter or window when postage has been paid to mail that item. The item is retained in USPS custody and is not handed back to the customer. The date printed on the PVI label is the date of mailing.

Save Money! Save Time! Pay Online!

Pay online or over the phone for free using your checking account. If you use the phone (IVR system) you will also need the Personal Identification Number (PIN) from your bill.

To make a payment now, go to Online Payments.

There is no need to write a check, hunt for stamps, or travel to a mailbox. You do not have to worry about mail delays or post office closures.

  • There is no charge for electronic check (e-check) payments.
  • Property Tax Payments can now be made via PayPal (with an online service fee of 2.35%).
  • You may also pay online by using a credit card (Visa, MasterCard, Discover or American Express). All credit card payments are processed through our payment service. Please be aware that there is a 2.35% service fee for payments.
  • The Treasurer-Tax Collector does NOT retain any portion of this fee. The fee is imposed by the credit card companies and cannot legally be absorbed by the County, therefore the fee must be passed on to the customer.
  • Electronic payments can be made 24/7 - Payments are accepted up until 11:59 p.m. Pacific Time on the delinquency date.

Online Bill Pay via Personal Banking Accounts:

Per R&T Code 2503.2 (e) electronic fund transfers shall constitute payment of tax, assessment, or redemption as of the date of acceptance when, but not before, the transfer has been completed by acceptance by the bank designated by the Tax Collector of the payment specified by the originator's payment order.


Tax Office Location

Hours of Operation

Make Tax Checks Payable to:

Mail Tax Payments to:

555 County Center - 1st Floor
Redwood City, CA 94063
Phone: (866) 220-0308
Fax: (650) 599-1511

Monday - Friday: 9 AM - 5 PM

Phone Hours are 9 AM - 5 PM (Monday - Friday)

Excluding all Holidays.

Sandie Arnott, San Mateo County Tax Collector

San Mateo County Tax Collector

PO Box 45878
San Francisco, CA 94145-0878