Any counter-letter whose purpose is to increase the price stipulated in the agreement for the transfer of a ministerial office is null and void.
Also void is any contract whose purpose is to conceal part of the price, where it relates to a sale of immovable property, a transfer of a business or client base, a transfer of a right to a lease, or the benefit of a promise to lease relating to all or part of an immovable property and all or part of the balance of an exchange or division comprising immovable property, a business or client base.