I think it depends on the local authority and their local empty property policies re CT. In Buckinghamshire we are lucky – vacant properties owned by a housing charity are exempt for CT. We obviously fill vacancies ASAP, but if there were a need to keep one empty for any reason the CT would still be nil. Worth checking local policies – I have found that sometimes a charge is made because the LA do not realise what their own polices are, or that the Almshouse is a charity.