For a very long time, Google did not approve of using PO Boxes as business listings. They even went as far as removing business listings which had PO Boxes as the address, and also not allowing the usage of PO Box in the address field at all.
Google still does not welcome PO Boxes with open arms and confer them the status of a physical location, but they have slightly relaxed the policy to better reflect how businesses and individuals use these virtual addresses in the real world.
Right now, the Google policy on PO Boxes is this:
“Do not create a listing or place your pin marker at a location where the business does not physically exist. P.O. Boxes are not considered accurate physical locations. If you operate from a location but receive mail at a P.O. Box there, please list your physical address in Address Line 1, and put your P.O. Box information in Address Line 2.”
You can list now your PO Box information in the second Address Line.
This must provide much relief to genuine businesses that extensively use PO Boxes to receive correspondence, perhaps because they operate in remote locations where mail delivery is limited or unreliable. It would also help businesses that offer services locally, but do not require a physical office, and home offices who do not want their home address to be listed online.