We refer to your email on 29 January 2014.
We wish to clarify that occupiers of HDB flats are not beneficial owners of the HDB flats. They are merely authorised by HDB to live in the HDB flat. Therefore, the HDB flat is to be excluded from the count of residential properties owned by your husband if he is only an occupier (not beneficial owner) of the HDB flat.
Hence for the scenario which you have quoted in your email: if your husband is a Singapore Citizen and do not own any properties (after the transfer of HDB flat has been completed), he will not be liable for ABSD if he solely purchase a private property. The purchase will be considered your husband first residential property.