Yes, assets acquired before January 1, 1989 are exempt from capital gains tax. This date corresponds to the entry into force of the IRS Code, approved by Decree-Law 442-A/88 of November 30. In order to avoid tax retroactivity, it was established that in order for such transfers to be taxed, it would be necessary for the assets in question to have been acquired and disposed of while the new law was in force and not before.
Thus, the gain obtained on the sale of a property from the personal assets of a natural person, the acquisition of which took place before the IRS Code came into force, is not subject to Personal Income Tax. However, even if exempt, the taxpayer must declare the transaction, with the respective values, in Annex G1 of Mod.3 of the IRS for the year of the transaction.
This is no longer the case if the property was acquired at various times after January 1, 1989. In this case, you have to carefully analyze each of the moments of acquisition in order to calculate the percentage of realization value attributable and whether or not you pay tax. For example, in the case of the acquisition of assets by “mortis causa” succession, the moment of acquisition of the assets is, as a rule, the moment of the opening of the inheritance, i.e. the date of death of the author of the inheritance, which means that if someone received a 10% share from their father who died before 01/01/1989, and a 10% share from their mother who died in 1990, and if they subsequently sell the property, only the first share will be exempt.
References: Article 5 Decree-Law No. 442-A/88 of November 30, Article 9(1)(a), 10(1) of the CIRS.
Source: jornaldenegocios