NAP stands for name, address, and phone number, the three basic pieces of information that identify a local business across the web. Consistency across every place that information appears (the website, Google Business Profile, directories, social profiles) matters more than it seems, because it's part of how search engines confirm a listing is legitimate and current.
Why small inconsistencies cause real problems
A business listed as "Smith Plumbing LLC" on one directory and "Smith Plumbing" on another, or a phone number that's outdated on an old directory listing, doesn't just look sloppy. Search engines use this data to cross-reference and confirm a business's identity and location. Inconsistency introduces doubt into a system that's specifically trying to confirm you're a real, single, stable business.
Where inconsistencies usually come from
Old directory listings that were never updated after a move or a new phone number, a business name that's been written slightly differently across different sign-ups, or a suite or unit number included in some listings but not others. Most inconsistencies aren't intentional; they accumulate over time as a business changes small details without going back to update everywhere it's listed.
It's connected to the duplicate listing problem
Inconsistent NAP data across the web is one of the more common root causes of a duplicate Google Business listing appearing in the first place, since some directories and data aggregators auto-generate listings based on scraped information. See how to handle a duplicate Google Business listing.
How to actually check and fix it
Search your business name across the major directories and platforms you can think of, and compare the name, address, and phone against your current, correct information. Fixing an inconsistency usually just means logging into that specific directory or listing and updating it directly.
Questions
Does this matter for a business that only has one location and no directory listings beyond Google?
It still matters between the website and Google Business Profile specifically, since those are the two places most customers and search engines cross-reference first.
How often should I check for inconsistencies?
Once thoroughly, then again any time the business changes a phone number, address, or legal name, since that's when new inconsistencies get introduced.
Do minor formatting differences, like "St." versus "Street," actually matter?
Modern systems are generally good at normalizing minor formatting differences. The bigger concern is a genuinely different number, name, or address, not stylistic variation in how the same information is written.