We have a 4 bedroomed chalet bungalow and an annexe attached where my disabled mother lived until she died 2 years ago. The annexe was exempt from council tax because of my mother's disability. My husband, who is 66 and retired is living in the annexe and I would like to know if we will have to pay the council tax for the annexe. We obviously pay the full amount of council tax for the main bungalow. Originally, the property was rated for council tax as one property.
The disregard for disability would have stopped when your mother died, so there will be a liability for CT from that date. You need to talk to the local authority about it.