What Does it Mean to Have a Fiduciary Responsibility to Your Spouse?

A fiduciary relationship is defined as:
“ where one person places complete confidence in another in regard to a particular transaction or one's general affairs or business. The relationship is not necessarily formally or legally established as in a declaration of trust, but can be one of moral or personal responsibility, due to the superior knowledge and training of the fiduciary as compared to the one whose affairs the fiduciary is handling.”

https://dictionary.law.com/Default.aspx?selected=745

There are some relationships that the law recognizes as being completely open and honest.  There is the famous example of Lawyer-Client privilege.  In order for a lawyer to be able to completely and honestly represent their client, there is a relationship there that the law cannot penetrate.  It gives the lawyer and the client the ability to be completely open and honest without fear of legal retribution.

Married couples also have a fiduciary responsibility to each other to be completely open and honest with each other.  This responsibility extends even when the couple is placed in an adversarial position from each other, whether it is while negotiating terms of a postnuptial agreement or even during a divorce procedure.

The fiduciary responsibility does not mean that you have to sacrifice your own rights for those of your spouse or your soon to be ex-spouse.  It does mean that during any discussion of assets, finances or any details related to the marriage or negotiations, there is an expectation that each spouse is being completely forthcoming, open and honest in their declarations.

If, at any point, a prenuptial or postnuptial agreement is challenged in court and the judge determines that the agreement is one-sided or the spouse has not completely lived up to their fiduciary responsibility, the agreement can be deemed void.  

Having a fiduciary relationship is a serious responsibility.  If it is violated, the consequences can be serious.