Pursuant to the State of California's Business and Professions Code, Professional Land Surveyor's Act, Section 8762 (b) a Record of Survey (ROS) is required when there is a material discrepancy or physical change that does not appear on any official map of record. Also the establishment of one or more points or lines that are not shown on any official map of record requires an ROS. Generally the most common reason a ROS is required is when the land surveyor is contracted to survey a lot or parcel that was created by deed without recording an accompanying map.
Example Record of Survey