Expatriates in Indonesia 

Postnuptial agreement  is another marital contract recognized under the laws and regulation in the Republic of Indonesia. It is a contract entered into by husband and wife within the course of their marriage. It is not valid retroactively and only applicable to property acquired after the contract legally executed.

As to other contracts under the legal system in Indonesia, both Article 1320 and 1338 of Civil Code are applicable to the postnuptial agreement. Those two articles are the basic rules for contracts in Indonesia, both for marital agreement as well as non-marital agreement.

Article 1320 of the Civil Code stipulates that in order to be valid, an agreement must satisfy the following four conditions: 1. there must be consent of the individuals who are bound thereby; 2. there must be capacity to enter into an obligation; 3. there must be a specific subject matter; 4. there must be a permitted cause. 

As for Article 1338 of Civil Code imposed that all valid agreements apply to the individuals who have concluded them as law. Such agreements are irrevocable other than by mutual consent, or pursuant to reasons stipulated by the law. They must be executed in good faith.

In view of the above two basic laws in recognizing the validity of the postnuptial agreement in Indonesia, married couples must abide those stipulation before they enter into the contract. Some required terms and conditions imposed by the Article 1320 of Civil Code are applicable thereto:

1. No consent is valid if it is granted based on mistake or obtained by duress or fraud. So, you need to have an informed consent from your spouse in order to enter into a postnup. A mistake does not render an agreement invalid unless such mistake pertains to the substance of the subject matter of the agreement. Duress against an individual who has entered into an agreement, provides grounds for nullification of the agreement, even if it was committed by a third party who does not benefit from the agreement. Fraud is form grounds for nullification of an agreement, if the fraud by one party is of such nature that it is apparent that the other party would never have concluded the agreement were it not for such deceit. Fraud is not be presumed, but must be proven.
2. Each individual is authorized to conclude agreements, unless he has been declared incompetent by law. The following individuals are incompetent to conclude agreements: 1. minors; 2. individuals under guardianship. Those individuals are incompetent to enter into agreements may claim for the nullification of the obligations, except for where the law excludes such power.
3. An agreement must at least have as a subject a matter a property whose nature is determined. The quantity of the matter needs not be ascertained, insofar such quantity can be determined or calculated at a later date. Future properties may be the subject of an agreement. An individual may not however, relinquish an inheritance which has not occurred or conclude an agreement regarding such inheritance, notwithstanding that he has obtained the consent of the testator.
4. Any agreement without a cause, or concluded pursuant to a fraudulent or prohibited cause, is not be enforceable. In the event that no cause is specified but that there is an existing permissible cause, or if there is a permissible cause other than the one specified, the agreement shall be valid. A cause is prohibited if it is prohibited by law, or if it violates morality or public order. 

As for the Article 1338 of Civil Code, the terms and conditions applicable to the postnuptial agreement are as follows: