Well if they are asking they don't know so I would just say "yes, I did, I paid my sales tax as a good citizen should, I could not live with myself knowing I did not give the sales tax on an item you already collected on when new and (depending on the year of mfg) that you collected from the other owners of this vessel, over and over again. Thanks for asking though, have a great day" the SLT is 7 years so you are past that but I am not sure it applies to a sales tax situation but I don't know. I had a leased truck once, I paid it off early but never transferred ownership from the lease co, when I sold it later I found I did not own it and had to jump thru some hoops to get it in my name so I could sell it. All went well and easy but at the Sec of State they asked if I had paid the tax, honestly could not remember because on a lease you pay the tax monthly, I had the lease for 2 years but did not pay all the tax. I told her yes, I did pay and she said that's OK, the State will check and if it was not paid I will be contacted. Well I never did pay and was never contacted, this was 5 years ago now. So I would just say yes and wait and see, or, if you want, you could dummy up a Bill of Sale from a dealer and show you did pay. Just don't say I told you how to do this.