Miller: Legal parcels are defined by the following criteria. Only one of these criteria have to be satisfied to establish a legal parcel.

1. A lot shown on a Final Map.  (Major Subdivision Map)
2. A lot or parcel shown on a Record of Survey approved by the Board of Supervisors or Planning Commission.
3. A parcel shown on a Parcel Map or Certificate of Compliance recorded in lieu of a Parcel Map.
4. A recorded Certificate of Compliance.
5. A parcel shown on an approved Division of Land Plat.
6. A parcel shown on a Lot legalization Plat used as evidence of legal parcel prior to a Certificate of Compliance.
7. A parcel shown on an approved Boundary Adjustment Plat.
8. A parcel described in a Grant Deed or other bona fide conveyance document recorded prior to February 1, 1972. The deed/document does not have to be in the name of the present owner. However, it must describe the perimeter boundaries only of the subject property and no other contiguous property. The legal description and County Recorder's information must be legible to County staff.  The Deed need not be an original or certified copy.
9. A parcel which is completely surrounded by lots already determined to have been legally created.

GlobeSt.com: What else should our readers know about legal parcels?

Miller: Properties within urban and suburban areas are generally legal lots approved by county planning departments. But don't assume anything. Land and lots in rural areas are a different story. Prior to February 1, 1972, many parcels were created by survey and sold without any Board of Supervisors' recognition or county approvals. Occasionally, this still happens. Some APN maps will show map and parcel numbers, which is prima facie evidence of legal parcel, but many parcels will have no map or parcel numbers, which is an immediate red flag to research the legal status of the parcel using the criteria above.