If your Unsecured property tax payment is not received or postmarked by the delinquent date, a 10% penalty and a $35.00 collection fee are added to your bill.

If your bill remains unpaid for two additional months, a monthly penalty of 1 and 1/2% begins to accrue. In addition, if a Certificate of Tax Lien is recorded by the County of San Mateo Tax collector, an additional fee of $13.00 will be required to release the lien. 

San Mateo County secured property tax bill is payable in two installments:

• The 1st installment is due and payable on November 1. However, you have until 5:00 p.m. of December 10th to make your payment before a 10% penalty is added to your bill.
• The 2nd installment is due and payable on February 1. The grace period on the 2nd installment expires at 5:00 p.m., on April 10. If the installment remains unpaid as of April 10, a 10% penalty and $40.00 cost is imposed.

Secured tax bills and Unsecured tax bills from the San Mateo County (CA) covers a "fiscal year." The fiscal year begins July 1 and ends on June 30 of the following calendar year.

The San Mateo County Assessor establishes the value of the unsecured property on January 1. This date is often referred to as the Tax Lien date.

The January 1 value is multiplied by the tax rate (usually 1% plus voter approved indebtedness). The unsecured tax rate is the prior year secured rate.

The term "Unsecured" simply refers to property that can be relocated and is not real estate. The tax is assessed against such things as business equipment, fixtures, boats and airplanes. If the unsecured tax is not paid, a personal lien is filed against the owner, not the property.

The term "Secured" simply means taxes that are assessed against real property, (e.g., land or structures). The tax is a lien that is "secured" by the land/structure even though no document was officially recorded. This means that if the taxes remain unpaid after a period of 5 years, the property may be sold to cover the taxes owed.