When buying a new house the municipality takes fees of registration (up to 5 % of the house cost). Is it possible not to tell them the real cost figure (lower price) so as to pay less registration fee? Is this fee considered as MOX (tax) which is Haram to gather from Muslims?

Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

If a government does not have any source of income to spend on social work and on common welfare, to establish hospitals, schools and pave roads or if its source of income is insufficient, there is no harm in imposing taxes on private property as long as there is no violation of public property. In that case, a person should not be a tax evader. In this situation, taxes would not be considered as toll since it is in the pubic interest. Allah knows best.