Most states offer a website an online look-up tool to see if a contractor’s license if current and what type of license the contractor has. Some deck contractors have basic carpenter licenses, while others may have a general contractor’s license.
A general contractor who builds decks usually has experience with other types of building construction that might be useful if you’re building a large deck, adding electrical or the deck features a roof, whereas a deck contractor with a basic carpenter’s license might not have the experience needed.
Also ask your deck contractor for proof of insurance. If they have liability and workers comp insurance, they’ll be happy to prove it. And, of course, check reviews and ask for references.