For the purpose of calculating the duties on gratuitous transfers, the properties, whatever their nature, are estimated according to their real market value on the date of the transfer, according to the detailed and estimated declaration of the parties, without distraction of charges, except, as regards the latter, what is stated in articles 767 et seq.
For properties that the owner has the use of on the date of the transfer, the actual market value mentioned in the first paragraph is deemed to be equal to the value free of any occupation.
However, if, in the two years preceding or following either the deed of gift or the starting point of the time limits for filing the declaration of inheritance, the properties transferred have been the subject of an auction, either by judicial authority or voluntarily, with the admission of foreigners, the duties payable may not be calculated on a sum less than the auction price, with the addition of all capital charges, unless it can be justified that the consistency of the properties has undergone, in the intervening period, transformations likely to alter their value.