For reference this issue is occurring in Scotland.

I have council tax bills including 3 from 2006/2007/2008 which I didn't pay. They went to sheriffs officers, I moved house and they lost contact - recently contacted them in an attempt to settle up old debt.

Paying these bills off now and have a payment plan setup with the sheriffs officers to do so. Bills have around £1,500 remaining from about £3,000 total. I received a letter earlier in the week telling me that the bills for these years had changed due to "Change in Tax Band". Turns out there was some work done to the property before I lived there, an extension that the council were not informed of which increased the size of the property. As my accounts for these years are still open and as the tax band has been changed for "the period of council tax existing" (they reckon these changes were done pre-1993) my bills have changed.

Firstly - is this legal? Can they just up and change the bill on me 6 years later because of something I didn't even do? And when I have a payment plan in place to pay the actual bill already?

Secondly - I assume if my balances had been settled in full already they wouldn't be able to touch me? My understanding of council tax accounts is that when they are paid the account is closed.

I have emailed the council department to contest the new charges, will update you when I know more.

when id the council go to the LVT to have the reassessment? If it was after you left then it is not claimable as it is not retrospective. You may have to speak to the tribunal office to get the exact rules and whether the council did apply for a change. If no application then there has been no change as it is not for them to decide.

It was very recently, as I said I haven't lived at this location for over 6 years. And the change was only done in August of this year.