Hola a todos! I recently bought a resale property in Valencia and thought everything was settled. However, last week I received a letter from the tax office, and to my surprise, it was a demand for additional tax! It’s the infamous ‘propuesta de liquidación complementaria’. I was stunned because we paid the tax based on the actual purchase price. Why the extra charge? I’m posting this to ask if anyone has had a similar experience and to share what I’ve learned over the past few days.
What is a Supplementary Property Tax Bill?
In simple terms, it means the tax agency (Hacienda) believes the price you declared for your property purchase is lower than their internally assessed ‘market value’. Therefore, they require you to pay the difference in Property Transfer Tax (ITP) based on their valuation, plus interest. This valuation used to be quite ambiguous, but since 2022, Spain has implemented a new official reference value (‘valor de referencia’), which can be checked on the General Directorate for Cadastre’s website. If your purchase price is below this reference value, it’s almost 100% certain you will receive a supplementary tax notice.

When we were buying the house, neither the real estate agent nor our lawyer specifically advised us to check this reference value; we were just told to pay the tax based on the contract price. And that’s how we fell into this trap. For example, let’s say you bought a property:
| Item | Your Situation | Tax Agency’s Assessment |
| Purchase Price | 200,000 euros | - |
| Official Reference Value | - | 220,000 euros |
| Tax Base Paid On | 200,000 euros | - |
| Correct Tax Base | - | 220,000 euros |
| Difference to be Paid | - | 20,000 euros |
Assuming the ITP rate in your autonomous community is 10%, you would have to pay an additional 20,000 * 10% = 2,000 euros in tax, plus a little bit of interest—which can actually be quite significant. The amount can vary greatly depending on the price difference.
What Should You Do After Receiving the Tax Bill?
After receiving the letter, you generally have two options: pay up or file an appeal.
Pay Directly: If the amount is small or you don’t want the hassle, you can choose to pay it. There’s usually a discount for paying within the specified period. This is the easiest way out, but it might feel a bit unfair.
File an Appeal: If you believe the tax agency’s reference value is significantly higher than the property’s actual market value, you can prepare materials to appeal. You’ll need strong evidence to prove your purchase price is fair, like getting a legally valid valuation report from an official appraiser (more on appealing property tax in Spain) or showing sale prices of similar local properties from the same period. The appeal process can be lengthy, the valuation report costs money, and there’s no guarantee of winning.
I’m currently debating whether to just pay it or to file an appeal. I feel this new reference value system is a bit unfair to buyers, especially those who genuinely found a bargain. Has anyone here on the forum successfully appealed? I’d love to hear your experiences! Also, can anyone recommend a reliable tax lawyer? Thanks in advance, everyone!