Under Portuguese Civil Law, the right of ownership is defined as the most absolute right one may have with respect to an asset. Provided the use of an asset is not incompatible with third's rights or with imperative law provisions, the owner of an asset may exclusively not only enjoy and dispose of it but also acquire its proceeds.

- Thus, the scope of the real estate ownership is governed by the three following principles:-- The ownership of a plot of land includes the ownership of the ground, the subsoil and the surface waters on it

--The ownership of a plot of land includes all the proceeds and income derived from the plot of land

 The ownership of a plot of land includes the ownership of all that is attaching to it under the principle of accession.
From a legal point of view, accession is a method of acquiring ownership whereby the owner of a principal asset becomes the owner of all that is incorporated therein.

According to this principle, the owner of a plot of land or building becomes the owner of any

constructions erected on his/her estate and of any improvements or transformations made to the building, regardless the identity of the person who erected the building and of the ownership of the building materials.

Purchase agreement, transfer agreement, notarial deed and registration

Acquisition of real estate requires a valid title, being the most common a purchase agreement. The purchase agreement, which is governed by Portuguese civil law provisions, is an agreement whereby the seller agrees to give an asset to the purchaser in return for the payment of a price.

The transfer of real estate has to be made by means of a public deed before the Public Notary. This notarial deed mentions the legal title of the transfer (e.g. purchase), the land registry's identification number of the property, and contains the signatures of the parties and, if necessary, the power(s) of attorney. Subsequently, the deed of transfer is registered with the Land Registry Office. This registration is an essential requirement for the transfer of ownership. Both the purchaser and the seller are entitled to register, although, in practice, the registration is usually made by the purchaser. A receipt certificate, stating the deed and time of registration will be provided. The exact time of registration is relevant, since where several registrations have taken place with regard to the same property, the oldest registration will take precedence.