The reduction is determined by forming a mass of all the assets existing at the death of the donor or testator.
Assets disposed of by donation inter vivos are fictitiously joined to this mass, according to their state at the time of the donation and their value at the opening of the succession, after deducting from them the debts or charges encumbering them. If the assets have been alienated, their value at the time of alienation is taken into account. If there has been subrogation, the value of the new assets on the day the succession is opened is taken into account, based on their condition at the time of acquisition. However, if the depreciation of the new assets was, by reason of their nature, unavoidable on the day of their acquisition, the subrogation is not taken into account.
A calculation is made of all these assets, having regard to the status of the heirs he leaves, what is the share that the deceased was able to dispose of.