Can a prenuptial or partition agreement be modified after it is signed?

Yes. The standard prenup contains a term providing for modification in writing at any time so long as both spouses agree. However, if one spouse does not agree to modify the document it remains in effect. A custom prenuptial agreement form can be drafted to contain any provision for modification agreeable to the parties. Normally, the draft states that a prenuptial agreement form can be modified in writing signed by both spouses.