First off, what is NAP? NAP is the shorthand for Name (or more typically business name), Address and Phone Number. For local businesses it’s a feature that helps tie all your local listings together.
It’s incredibly important and should be added to sites and directories that link to you. More importantly, it should be consistent across the sites and directories that are linking to your business. This can be hard though, especially if your business has been around for a while and is just now either getting an online presence or you’ve moved at some point recently.
Imagine this situation, your company ABC Cleaners has been around for a while. When you first opened you listed in the Yellow Pages as ABC Cleaners Inc., but at some point you moved and later dropped the Inc. You now probably have two listings unless you’ve really been keeping on top of everything (in which case kudos).
What’s going to show up is ABC Cleaners Inc. at address 1 and a second business ABC Cleaners at address 2. Worst case you could even have 3 or more listings with a mixture of those options. Yellow pages doesn’t know if you’re the same company, they’ve just found info on this new location and are doing their best to stay up to date by adding the second location in. This causes you to compete with yourself, gives a bad customer experience if they try calling your old number or visiting your old address and can negatively effect your rankings.
Ensuring you’re keeping consistent NAP across listings and directories can be a pain but is well worth it in the long run.