This has always been an important distinction, as only furnished lettings entitle you to the valuable annual wear and tear allowance of 10% of the rents. Now it is definitely worth reviewing whether you could show the property is furnished given that the renewals basis for replacing items in commercial or residential properties let unfurnished ceased from 6 April 2013.
It has recently become apparent that it is not always too difficult to show that a property is let furnished. HMRC guidance is that a property is furnished if it includes some (but not necessarily all) items that a tenant or owner-occupier would normally provide in unfurnished accommodation. That vague statement is then amplified and indeed the 10% allowance should be claimable where the property contains sufficient furniture, furnishings and equipment for normal residential use.