This is only currently applicable to New developments/promotions. i.e properties that are being sold for the first time. This puchase tax is NOT the standard ITP (impuesto de Tramisiones Patrimoniales) BUT is actually IVA (VAT). The central government announced that this rate will be increased to 10% in 2013 from the rate of 4%.
There is speculation that the governments of autonmous areas such as Andalucia etc may follow a similar pattern and increase the ITP purchase tax from 8% (property below value of 400.000€ to 10%. But as yet this has not been announced and in my opinion unlikely to be annouced at this stage for 2013.