What is an overlay area code?
An overlay area code is a new area code added to the same geographic region as an existing code, so two or more codes serve the same place.
How overlays work
When a region runs low on phone numbers, state regulators can relieve it with a geographic split, an overlay or a boundary change. FCC rules describe an all-services overlay as a new area code introduced to serve the same geographic area as one or more existing area codes. Under those rules, an overlay cannot be put in place unless ten-digit dialing is required for every call within and between all area codes in the region.
Why it matters for sales teams
In an overlay region there is no single local area code. Residents and businesses there may have numbers in any of the codes, and all of them are local. A team choosing local numbers for that region can pick from any of its codes.
Overlay vs split
In a split, the region is divided and part of it moves to a new area code. In an overlay, the boundary stays the same and the new code is stacked on top, so existing numbers keep their code.
This is a general definition, not legal advice.