The County Assessor has the duty to "discover" property which should have been listed during the January listing period.
When property is discovered, the taxpayer is notified in writing and has a period of thirty days to challenge the validity of the discovery. There is a statutory five year presumption, meaning that taxes will be assessed for the current year plus five previous years unless the owner provides documentation which indicates a shorter time period is appropriate. Statutes require that a 10% penalty be added for each listing period in which the property was not listed.
Once the discovery becomes final, a tax bill is generated in the current year levy, and the taxpayer has until January 5th to pay the bill without incurring additional interest charges.