According to Arizona Law:

A new subdivision is created when a parcel is divided into 6 or more smaller parcels as long as any one of these parcels is smaller than 36-acres.  The Subdivision Regulations contain the procedures for creating a new subdivision and the purpose of the Subdivision Regulations is to implement the Comprehensive Plan Goals of promoting orderly growth, providing for adequate roads, utilities, water and wastewater treatment, ensuring that structures are not built in areas subject to flooding and ensuring an accurate legal description when dividing a large parcel into smaller lots for sale.

ANYONE dividing parcels should always check to see that they are in compliance with local laws, zoning and variances.  For more information, contact your County office:

Maricopa County - http://www.maricopa.gov/planning/Resources/Regulations/Subdivision.aspx

Pinal County - http://pinalcountyaz.gov/Departments/PlanningDevelopment/Pages/Home.aspx

Cochise County - http://cochise.az.gov/cochise_planning_zoning.aspx?id=302

Apache County - http://www.co.apache.az.us/Departments/CommDevelope/Planning.htm

Yavapai County - http://www.co.yavapai.az.us/DevServ.aspx

Gila County - http://www.co.gila.az.us/index.html

Navajo County - http://www.navajocountyaz.gov/pubworks/pz/