Under Belgian law, if there is no marriage contract, the spouses are governed by the statutory prenuptial system of separation of assets with a community of acquisitions. In order to deviate from the statutory default regime, the parties must enter into a marriage contract pursuant to which they select a specified regime or create their own terms.

The contract must be drafted by a Belgian notary as a formal deed. The notary has a duty to be objective and to fully inform the parties about the terms and consequences of the agreement. Indeed, the notary may be liable for damages if the agreement is unbalanced or if there is a conflict of interests. 

The marriage contract may not deviate from the Belgian rules governing public order and common decency, from the rules setting out the respective rights and duties of the husband and wife, or the rules on managing the communal estate and assets.
Spouses cannot waive the rights to maintenance before the dissolution of the marriage (Article 301, Section 9 of the old Belgian Civil Code).

A party who cannot appear in person may be represented by a proxy by means of a special power of attorney executed before a notary. 

The marriage certificate must provide the following information: the date of the contract, the name and address of the notary who drew up the contract, and the type of marriage contract. Failing this, any clauses derogating from the statutory system may not be applied to third parties who engaged in contractual relationships with the husband and wife without knowledge of their marriage contract. 

There is no requirement to disclose assets as to a premarital agreement, but one spouse may request disclosure of all movable and immovable property, as well as all debts, of the other spouse for a post-marital agreement that overrides a previous contract pursuant to the Belgian Civil Code, Article 1394, paragraph 2.
Any transfer of real estate in connection with a marriage contract must be registered with the mortgage registration office. 

All marriage contracts must be registered with the Central Register of Marriage Contracts. If an agreement deviates from the proportional distribution rule or provides for the appointment of an heir, it must also be registered with the Central Register of Last Wills and Testaments. 
If one spouse is a merchant, within one month after the marriage contract is drawn up, the marriage certificate must be sent to the clerk of the Commercial Court in whose jurisdiction the spouse in question is listed in the trade register. 

The parties may change their marriage contract during their marriage.

Foreign Pre- or Postnuptial Agreements
Recognition of foreign prenuptial and postnuptial agreements in Belgium is governed by the Belgian Code of Private International Law, except insofar as the matter falls within the scope of the European Union's Matrimonial Property Regulation No 2016/1103. Both such laws require compliance with local public policy standards. 

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