Does Cohabitation constitute a change of circumstances to modify support?

Yes. A supported spouse's cohabitation with a person of the opposite sex gives rise to a rebuttable presumption of proof of decreased need for spousal support.

Under the family code,"Cohabitation" means more than a roommate relationship; the statute contemplates a personal, romantic relationship. 

That being said, even a simple boarding arrangement under which expenses are shared or rent received may reduce the need for support and thereby constitute changed circumstances. Cohabitation may reduce the need for spousal support because sharing a household reduces the expenses of the supported spouse. Additionally, the cohabitant's income may be available to the supported spouse. 

Courts have found that an earlier determination that a spouse was merely a roommate does not preclude a court from later recognizing a change in the relationship and determining that the roommates are cohabiting. The change in the relationship constitutes a change of circumstances warranting a review of the existing spousal support award. In re Marriage of Bower, 96 Cal. App. 4th 893, (2d Dist. 2002).

A supporting spouse's cohabitation does not have the same impact on a case. The income of a supporting spouse's subsequent spouse or nonmarital partner will not be considered when determining or modifying spousal support. FC § 4323 (b). The provision was intended to exclude both direct and indirect consideration of new mate income. In re Marriage of Romero, 99 Cal. App. 4th 436, (4th Dist. 2002). 

While the statute does not expressly address expenses, it has been held that not only must new spouse income be disregarded but also the  additional expenses resulting from the remarriage. In re Marriage of Romero, 99 Cal. App. 4th 1436, 122 Cal. Rptr. 2d 220 (4th Dist. 2002).

If you are receiving spousal support and are considering moving in with a friend/partner, keep in mind that your ex could make a motion to reduce support. If you are interested in learning more, you can contact me at Amanda@gordonfamilylaw.com for more information.