A business gets a new manager, who cannot find the login for the existing Google listing, so creates a new one. A year later someone else does the same. Now there are three versions of the business: one with the old address and eleven reviews, one with the current address and two reviews, one with a phone number that belongs to a member of staff who left.
This is one of the most common problems in local search and one of the least discussed, partly because it is invisible from the inside. You search your own business, see a listing, and assume it is the listing.
Why it costs you
Reviews get split. Eleven reviews on a dead listing and two on the live one is much weaker than thirteen in one place. Reviews are among the strongest signals for local ranking and among the strongest influences on whether a human picks you.
Search engines lose confidence. Consistent name, address and phone number across the web is a signal of legitimacy. Three conflicting versions is a signal of uncertainty, and uncertainty suppresses ranking.
Customers reach dead ends. Somebody calls the old number and gets nothing. They do not call again through a different listing, they call your competitor.
You cannot manage what you cannot see. Reviews land on a listing nobody monitors, including complaints, sitting unanswered where every future customer can read them.
How duplicates happen
Staff turnover with no handover of the login is the biggest single cause.
Moving premises without updating the existing listing produces two, one at each address. Being auto-listed by data aggregators from public records creates listings nobody deliberately made. Agencies creating a fresh listing rather than requesting access to the existing one is common. And a business with a slightly different trading name in different places -- with and without Ltd, with and without the ampersand -- can end up split simply through inconsistency.
Finding them
Search your business name and look past the first result. Search your phone number in quotes. Search your street address. Search old names the business has traded under, and the names of previous occupants of your premises if you took over a location.
Then search on a map view rather than a normal search, and look at your street and the streets around it. Duplicates often sit at slightly wrong coordinates, which is exactly why you never see them.
Check the other places that carry listings independently -- the major directories, the industry-specific ones, anywhere a former staff member might have registered you.
Cleaning up
Decide which listing survives first. Usually it is the one with the most reviews, provided the address is correct or can be corrected. Reviews are the hardest thing to rebuild, so protect them.
Claim everything you can. For listings you can access, you can mark duplicates for removal or merging. For listings you cannot access -- because they are tied to an old email nobody has -- there is a recovery process where the current owner can request access, and it is worth going through properly rather than abandoning the reviews.
Where a genuine merge is possible, take it, because merging preserves reviews. Where it is not, remove the duplicate rather than leaving it.
Then make everything consistent. Pick one exact form of your name, one address format, one phone number, and use that same version everywhere without variation. This is tedious and it is the part that actually fixes the problem.
Keeping it fixed
Put the login somewhere the business owns, not somewhere a person owns. A shared business account, with more than one person having access, and the recovery details recorded.
That single change prevents the most common cause. Most duplicate listings do not exist because anyone made a bad decision -- they exist because somebody could not get in and needed the listing to work today.
If you engage anyone to manage your marketing, give them access to your listing rather than letting them create their own. The listing is an asset of the business. It should not leave with the agency.