Articles 1147 and 1148 B.W. provide that a debtor is released from his obligations if he can show that his non-performance is due to FM.

Defined by case law as "insurmountable and unforeseeable impediment to the fulfillment of an obligation", which is not the debtor's fault.

Note: in certain cases, courts are willing to broaden definition to any situation making performance "reasonably impossible".

This is not mandatory law and parties are therefore free to agree otherwise.

No, it is implied in every contract.

However, parties are in principle free to exclude FM from their contractual relationship, or – as the case may be – to modify the definition, conditions and effects of FM (except in some limited circumstances, like in consumer contracts).

None – it is however advisable to notify the other party as soon as possible when confronted with an FM event.

This notification requirement has been included in the draft bill on the introduction of a Book 5 "Obligations" in the new Belgian Civil Code (which was approved by the Belgian Justice Committee in March 2022 but is still to be voted by the Belgian Parliament).

Generally, the party relying on the FM event also has the burden of proving the FM event by producing evidence of the impact of the event.

Depends on the specific wording of the FM clause.

However, when there is an actual situation of FM, which requires an insurmountable and unforeseeable impediment to the fulfillment of an obligation, there is not much the debtor can do to mitigate.

In the event of a temporary impossibility, the debtor's obligation to deliver is suspended until the FM situation disappears and the performance of the obligation is thereby made possible again. The counterparty will in turn also be entitled to suspend its own obligations (based on the risk theory).

Following such suspension, an extension of time for performance may then be granted automatically or by agreement. In case the FM event is permanent in nature, the debtor will be freed from its contractual obligation. Such termination of contractual obligations may give rise to an obligation to refund the other party.

Prohibition of abuse of rights: courts may prevent a party from abusing its right to enforce a contract in a situation where the contractual balance has been significantly disturbed due to a considerable change in market conditions. However, it is to be noted that hardship (i.e., an unexpected event leading to a more onerous, more costly or less profitable performance) and the theory of "imprévision" (i.e., the French legal provision which consists of disequilibrium between reciprocal obligations due to an unexpected event allowing the revision of the contract) are in principle not recognized under (current) Belgian law (except under public procurement contracts and contracts subject to the CISG). This may, however, change in the very near future as the draft of Book 5 "Obligations" in the new Belgian Civil Code does provide a legal basis for the theory of "imprévision". Parties are of course free to include a hardship clause in their contract.