VPT

Valor Patrimonial Tributário — the taxable value of a property as assessed by Finanças. It is usually well below market value and appears on the caderneta predial.

Where people slip: IMI is calculated on the VPT, not on what you paid — so estimating your annual bill from the purchase price gives the wrong number, usually far too high. The VPT also feeds part of what you pay in IMT at purchase, and the thresholds for IMI exemptions are expressed in VPT, not in price.

Do this: ask the seller for a recent caderneta predial before you commit, and read the VPT from it. Note that a renovation or a re-assessment can raise the VPT afterwards — the number you see today is not fixed for life.