First I wouldn't buy a house for that price, it is just overpriced and not at a place I'd enjoy living. And the second part is that you don't need to declare the real price you pay.
Maybe in your country this would be a problem, around here it isn't. The only sideffect is that legally you have to offer the neighbors the chance of buying a house/land for the public price you are selling.
I live in Portugal too. I see your point, but underdeclaring property prices seems risky. Beyond the tax implications, it could draw BCFT scrutiny, especially for large transactions. Paying a significant amount under the table or using untraceable funds like Monero might raise red flags with notaries or registrars, who are obligated to report anything suspicious. And wouldn’t the IMT and stamp duty still need to align with the official declaration?
Will answer through a different way.
