The article linked below was published on April 30, 2025, so it has some probability of being accurate. First, some of the money quotes from it:
"In Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Hawaii, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Mississippi, Missouri, Montana, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Oklahoma, South Carolina, Tennessee, Vermont, Washington, West Virginia, and Wisconsin you don’t have to register your kayak or canoe."
"While you don’t have to register your kayak or canoe in the states above, you may still be required to pay any local launch use fees." (This is certainly the case in Connecticut. Launch permits are required by many towns with water access, and only town residents can get the permits.)
"If you’re a short-term visitor to a state that requires registration, you often don’t have to register your kayak. Local launch permits and fees still apply." (In other words, the rules can vary from state-to-state for non-resident/tourist paddlers. I've never worried about it.)
"Adding an electric trolling motor almost always means you need to register your kayak or canoe. . . . Adding a sail to your kayak may also change requirements." (Again, the rules can vary from state-to-state.)
Registering your kayak can feel like an intimidating task, but we’re here to demystify kayak registration. From which states do and don’t require
paddlingmag.com