A legal act suffers from a defect, but is considered valid as long as the person for whose protection the invalidity is established does not allow this invalidity. The effects of invalidity occur only at the moment when the objection is raised (Section 586 et seq. of the Civil Code).

Relative invalidity is a milder form of invalidity. It serves to protect the interests of the individual, not public order, and its application depends solely on the will of the authorized person. If this person does not raise the objection of invalidity, the legal act remains effective as if it were completely valid.

Typical cases of relative invalidity are contracts concluded in error, under duress or threat, legal acts without the consent of the spouse where it is required, or agreements showing signs of usury or unreasonable inequality between the parties. In these situations, the legal act gives rise to legal consequences until the person concerned invokes the invalidity.

The form in which the objection of relative invalidity can be raised is not specified – it can be raised both in court proceedings and informally towards the other party. Only the person for whose protection the invalidity is introduced is an authorized person. The law does not set a specific deadline for raising the objection, but it is generally accepted that the right to invoke relative invalidity expires within the normal limitation periods.

If the objection is raised properly and in time, the legal act is annulled from the beginning (ex tunc). If the objection is not raised, the legal act remains valid and effective. Unlike absolute invalidity, relative invalidity can be cured retrospectively if the reasons for the invalidity cease to exist or if the authorized person subsequently expresses his consent to the contract – for example, if he subsequently confirms a previously defectively concluded contract.

Relative invalidity therefore maintains a balance between the protection of the weaker party and the stability of legal relations. The law here protects the active participant, who has the opportunity to appeal the invalidity, but not the one who remains inactive.