If your divorce agreement provides for spousal support it will also provide for the events that can cause it to be terminated. Spousal support also known as "maintenance" or formerly known as "alimony" exists based on the concept that one spouse needs financial assistance from the other based upon a difference in income, earning capacity, medical condition, not having worked or having given up work opportunities during the marriage or any similar combination of reasons.
New York now utilizes a maintenance formula for the calculation of a guideline amount of support as well as guideline duration. A Google Search will locate the calculator.
Generally the longer the marriage, the longer the support may run. The greater the income difference, the more likely a larger amount of support. There are many factors that the court must analyze but the first step is to usually look at the guidelines from the formula. The court as well as the parties may deviate from the guidelines for many different reasons. However, this blog is not about the deviation rather it is about whether moving in with someone may terminate the obligation to pay or receive spousal support.
NY has a statute (Domestic Relations Law Section 248) that states that maintenance terminates if the recipient is "habitually living with another person and holding himself or herself out as the spouse of such other person, although not married to such other person..." Over the years it has been widely recognized that it is very difficult to prove that a person is "holding out as the spouse" even if living with the other person. The concept of "holding out" may mean proving that the person refers to themselves as "Mr. & Mrs." or tells people that they are married. Years ago private investigators would try and get access to hotel registration forms to try and prove this.
Recognizing the difficulty, many attorneys will draft alternative language in divorce settlement agreements so that the proof is not as difficult. I have seen many agreements that state if you live with someone else (not related by blood or marriage) for a period of 30 consecutive days or 180 non-consecutive days in a one year or 18 month period it will be presumed to be cohabitation and a maintenance terminating event. A variation of that concept is to add living together in an "intimate relationship" or "sharing financial support".
Even with less demanding language it is still difficult to prove. People can stay overnight and not be living together; people can maintain a second residence that they utilize a few days each month (thus the reason for the cumulative period) but still very difficult to prove that the number of days has been met. Proving who pays which bills may require subpoenas.
Clearly re-marriage or death of either former spouse will terminate maintenance payments, although there could be an insurance requirement of the paying spouse.
Maintenance provisions are a landmine and complicated and should be carefully analyzed and drafted in a settlement agreement. Likewise the recipient spouse should disclose to their own attorney if they believe they will be entering into such a relationship before the settlement agreement is signed. Maybe instead of spousal support (which can be terminated) a better financial distribution can be negotiated. The need for highly experienced matrimonial counsel cannot be overstated.