Check with the NVDC if you think you have a valid USCG Documentation, if you tell them that you also have a state registration in any state on that same vessel, they will invalidate your USCG Doc. which also invalidates your First Preferred Ship Mortgage filed with the NVDC if you have one. This will piss off your lender if you have one. And if you insured your boat as being US Flagged vessel i.e. USCG Doc. your insurance may be invalid as well. You can probably coast for years like this but have one injury accident and/or one significant damage claim you may be dead meat.
As I've said previously, private boats and yachts permanently moored in a state with a "personal property tax" (like Washington) requires all owners whose boats are USCG Documented to go to their state's' tax office and sign up and pay the tax. (Oregon had no "personal property tax when I lived there) Most state tax office employees know nothing about NVDC rules. Do not let them talk you into a state registration!!! Don't argue with them!!! Just ask for a supervisor.
When I was a flight instructor at Boeing Field where I parked my little Piper when not giving lessons. The friendly Washington tax cops tried to tax my business property (the little Piper). Too bad, they lost the argument. I was already paying them rent for the tie-down.