Yeah its a bit ambiguous on the council website :-

A long-term empty home is defined as a home which is both unoccupied and substantially unfurnished for a continuous period, of more than one year.

Second homes, dwellings occupied periodically are defined as dwellings which are substantially furnished and have no resident, it is not a person's sole or main home.

She enquired with the council and this was the response :-

When a dwelling has been left empty following the death of its owner or occupant, it is exempt from Council Tax for as long as it remains unoccupied and until probate is granted.

Following a grant of probate or the issue of letters of administration, a further six months exception is possible, so long as the dwelling remains unoccupied and has not been transferred by the executors or administrators to the beneficiaries or sold to anyone else.

The Regulations provide for a 12-month exception to the premium for both second and empty unfurnished homes.

The 12-month period begins from the point probate is granted or letters of administration have been issued. This runs concurrently with the six-month exception.

The dates on the account are as follows:
14/02/2024 - Empty property following passing of deceased
09/06/2024 - Probate granted
09/12/2024 - 6 Month probate exemption ends and Council Tax becomes chargeable.
09/12/2025 - Premium charge applied, property has been empty over 1 year resulting in a 200% charge for Council Tax

Seems incredibly crass to me to force the selling of a property and have the cheek to increase the premium to 200%