Luxury vehicle tax runs out in 3 months, what happens?

Don't know about DD but if you buy the tax for a year the rate is calculated at x mnths of the high rate and y mnths at the low rate, add them together and there's you tax bill. So I assume (but not certain) that paying by DD, the above calculation will be done and then divided by 12 to get your monthly payment.
If that is correct then the DD won't 'automatically adjust' but you will be getting the mixture of high rate and low rate spread over the year.

Had the same situation with a car I bought, because the luxury tax ran out in 5 months I could not tax it via monthly direct debit, had to pay for 6 months or 12 months in full but the price took in to account the change in price after the 5 months.

Great info, thanks

Again, thanks.

And then… I passed on the info and: what would you do?

Ffs! Tell him to make his own mind up! He’s not going to prison for making a duff decision, and I can’t predict the future..