What is the ruling of Sharia on some contractors resorting to declaring in sales contracts that they are barter contracts (barter of real estate for real estate or movable property for real estate) before the official notary to avoid exorbitant tax costs, even though they are in fact sales contracts in which the seller received a sum of money?

It is permissible to use stratagems to reduce taxes if the state levies them unjustly and spends them on things that are not Islamically legitimate, because this falls under the category of removing oppression and warding off harm. However, if the state imposes them due to the weakness of its public resources in fulfilling the needs and interests of the nation, then it is not permissible to evade them or to use stratagems to reduce them, because collecting them is necessitated by public interest.