If the reference value (“valor de referencia”) or the tax authorities say the flat is worth more than I paid, do I have to pay more property transfer tax (ITP)? How do I appeal?

If the flat has a reference value

A flat normally does have one. ITP is then paid on the reference value, unless the price or the value declared in the deed is higher. In this case the tax authority does not carry out a valuation check (“comprobación de valores”) by other means, such as the mortgage valuation, because the tax base is set by law.

In February 2026 the “Tribunal Constitucional”, Spain's Constitutional Court, ruled that this system is constitutional, because it allows any evidence to be used to show that the flat is worth less. A contradictory expert valuation cannot be used against the reference value, because it is not a valuation check by the tax authorities. There are two ways to dispute it, depending on how you filed the return:

• If you paid on the reference value, you can ask the tax authority to rectify your self-assessment as long as four years have not passed since the deadline for filing it. If you succeed, the difference is refunded to you with interest.
• If you declared the price and the tax authority has issued an assessment based on the reference value, you can lodge an application for review (the “recurso de reposición”) with the tax authority itself, or a claim with the “Tribunal Económico-Administrativo Regional de Cataluña”, the regional tax appeals tribunal, within one month of notification.

Before deciding on the rectification or the application for review, the tax authority asks the Cadastre for a report, which is binding on it. You will have to prove that your particular flat is worth less because of its condition, its defects or its location, normally with an expert report comparing it with actual sales. If the valuation carried out for the mortgage is lower, it can serve as further evidence.

When there is no reference value

If the flat has no reference value, or the Cadastre cannot certify it, ITP is paid on the highest of the price, the declared value and the market value. The tax authority can check that value using the means provided for in the “Ley General Tributaria”, Spain's General Tax Act, including the valuation carried out for the mortgage. This is uncommon for flats nowadays, because most have a reference value. The “Tribunal Supremo”, Spain's Supreme Court, has laid down these rules in several judgments, including some from February 2026:

• A significant difference between the declared value and the mortgage valuation is enough for the tax authority to check the value, without first having to prove that there was fraud or concealment.
• The tax authority has to explain why it is using that method and why it believes the valuation reflects market value.
• The valuation is not an unchallengeable truth. You can rebut it with a sound expert report, with identified comparable homes and verifiable sources.

You can make representations with that report when the tax authority notifies you of its proposed valuation. When you receive the assessment, you have one month to request a contradictory expert valuation, a procedure in which an expert appointed by you tests the tax authority's valuation. Within that same month you can appeal against the assessment to the tax authority itself or to the regional tax appeals tribunal and, later, to the courts.

Before appealing

• The prudent course is to pay on the reference value and then request rectification. If you declare only the price, the tax authority will assess you for the difference with interest and may impose a penalty.
• Do the maths before commissioning the expert's report. At 10 %, every 10.000 euros of difference in value means 1.000 euros of tax.

In the rest of Spain the system is the same, except in the Basque Country and Navarre.