An HMO (House of Multiple Occupation) is a type of property that was either built or changed so that it can be rented out to people who are not living together as a single household.
For guidance, see Houses in Multiple Occupation on gov.uk
Definition of a HMO in Council Tax legislation
A property that is occupied by one or more tenants each with their own tenancy agreement for part of the property. However, each is not liable, whether alone or jointly, to pay for the dwelling as a whole. Generally a house in multiple occupation will be a property occupied by more than one household and more than two people, and may include bedsits, shared houses and some self-contained flats
If the above is determined then it is the owner that is liable to pay Council Tax.
As the owner of an HMO property you are required to hold a licence in order to continue to let the property legally. Find out about licences for HMOs.
Any disputes are not reason to withhold payment of Council Tax. You are advised to pay as billed.
Useful information provided by the Valuation Office Agency (VOA)
GOV.UK provide Guidance on the recent change to how Houses in Multiple Occupation (HMOs) are valued for Council Tax in England.