I’m going through this right now as well. In the process of buying out a US Bank lease on my Tundra and they seem to agree with me that they paid the tax at the time of the lease and I don’t get double taxed. (I did get tax credits on this at the time of lease). Even the payoff quote they gave me does not include additional sales tax.
Also referencing this which does seem to suggest if it is just being retitled to lessee there is no tax due (section C) -Texas Administrative Code
But I will admit I am thoroughly confused by the whole thing. I’m planning to buy the Truck as the lease is up at the end of the month and it’s worth a whole lot more than the buyout but will probably trade it on something else shortly.