The Assessor’s Office periodically reviews the accuracy of our property records to ensure all properties are fairly and equitably valued. The Assessor’s Office utilizes technology to compare recent and older street and aerial photography to find unreported changes to property. Upon finding changes that increase or decrease the Full Cash Value equal to or greater than 15%, the Assessor’s Office will send a letter to the owner reporting the livable and non-livable square footage of the property before and after this canvassing process. The letter will also include information about Rule B and what appeal rights the owner has if they wish to challenge the accuracy of our data update.

The County has 1.2 million properties and we have been unable to review this section of properties for the last several years. Our office is always striving to ensure the most accurate property records possible and this review process is an example of using new processes and techniques to make that possible.

Although you may have not made changes since you owned the property, the prior owners may have made changes that we were unaware of. Due to our county's size and the limited number of staff, we are not able to review every parcel annually.

The Assessor's office re-values your property each year based on the sales market and the improvements on the parcel. Due to the records on your property not being updated for several years, we have recently been able to review your area and make the necessary changes to bring our records up to date.

We have aerial photographs and measuring tools available on our computers. The image quality used is specifically designed to allow a complete and accurate review in the office.

Although each property is affected differently, this notification will result in a recalculation of the property's Limited Property Value (LPV) on which property taxes are set. It is difficult to determine how this will affect the property taxes at this time, as the statutory B-rule ratios are reset at the beginning of each year for every property class. The changes made to the property will be in effect for a future tax year and the statutory B-rule ratio will be set upon completion, review, and approval of the Full Cash Values (FCV) by the Arizona Department of Revenue. For this reason, it is recommended that property owners review the current assessment of their property and notify our office immediately if there are any discrepancies.

The Assessor's office is required to locate, identify, and classify all properties in Maricopa County. Part of this requirement is to assure properties are accurately listed in order for each property to pay their fair portion of the property taxes needed to provide services.

Per Arizona law, the Rule B calculation sets the limited property value at the level or percentage of the full cash value that is comparable to other properties of the same or similar use or classification. If a property was partially or fully omitted from the rolls and/or changes were made to a property, the LPV will be set to the average of that property class (AZ Statute 42-13302). For example, in 2018 tax year, the average LPV was 74% of FCV for primary residences. Therefore, if your primary residence qualified for a B rule, the LPV should be 74% of the FCV.

The Rule B calculation is required when the change in the full cash value of a property is equal to or greater than 15% due to permitted construction or a canvass that recognized a change to improvements on a parcel. It is also used to calculate the LPV for new parcels due to splits and consolidations.

For more information on our B rule policy, please view the Rule B Calculation- Revised (PDF) document.

There is a short video on the Maricopa County Assessor's website that can help explain how a value is formed on a property. The Assessor's office re-values your property each year based on the sales market and the improvements on the parcel.

The Assessor's office re-values your property each year based on the sales market and the improvements on the parcel.

If the room is heated and cooled with the rest of the property it is considered an addition. If there is a wall unit (A/C unit) it will still be counted as an addition but a lower quality classification will be given. Arizona rooms are given a lower quality than an average addition.