Ido,
It depends what you are buying and what for.
If a company purchases second hand residential property the tax is the same as for a private individual – namely 10% ITP (plus notary and registry fees).
If you are buying new build, then 10% VAT, which might be tax deductible to some extent – it depends on how you structure it.
If you are buying second hand to refurbish and sell, then 3% ITP.
If you use a Spanish SOCIMI structure, then you pay very little tax.