“I’m still married, but now I have a live-in girlfriend. We both have kids. What does this mean, legally speaking?”

Whenever a married couple separates – especially if there are young children involved – it’s best to document any custody and parenting arrangements, even if they’re only to be used on an interim basis. A memorialized (documented) separation agreement will lay out what happens with custody of and access to children, their primary residence and what should or should not be paid in support. Other issues typically dealt with in a separation agreement will be who has rights to the marital home, how finances are to be arranged in the new marital status, and, on a final basis, who gets what property.

Couples separating amicably may not think they need the formality of a separation agreement. However, schools, banks and healthcare providers may need some kind of formal documentation in changed or fluid custody situations. A formal agreement which is made when things are going well can benefit everyone involved when issues arise or when one former spouse takes on new responsibilities – or enters into a co-habitation situation with a new partner.

The trickiest issue may be the occupation of the marital home. The mortgage, property taxes, utilities and maintenance will have to be paid, regardless of who is living in the home. And the value of the home accrues to both partners in a marriage even if it is owned (on the deed) by one person. Both people in a married couple have a right to possession of the marital home until this is changed by court order or agreement.

Children need certainty and stability, and to achieve this, parents need to collaborate in parenting. A written agreement can lay out rights and responsibilities for parents. Just as fences can make for good neighbours, a good separation agreement can help a separated couple to avoid conflict and unintended consequences.

Introducing a new partner into the mix

Embarking on a common-law relationship before the previous marriage has been dissolved is fraught with potential problems, especially if there are unresolved issues from the marriage. A soon-to-be ex-spouse could take possession of the matrimonial home; support obligations, especially if they change, can disrupt financial plans; and who will be allowed to pick up the kids from school or daycare?

A cohabitation agreement with a common-law spouse can be a good way to help define rights and obligations of everyone involved. What role will the new spouse play in the disciplining of children? What contribution will a common-law spouse make to the household expenses? If the new partner is also still legally married, what impact could this have on the household?

(The truth is that, especially when children are involved, having a detailed conversation about just how the new, blended household will work is a good idea, regardless of whether one or both partners is still legally married or not. Setting realistic expectations and guidelines at the outset can prevent a lot of distress later.)

Common-law couples and married couples are not created equal in law. (So far, there are no special provisions in law to accommodate polyamory relationships, which makes it extra-important to document agreements in those cases.) Property rights apply to married couples, but not to common-law couples. Child and spousal support can apply to common-law couples, even if you don’t have biological or adopted children together.

The bottom line? When separating, it’s always a good idea to document any arrangements right from the start. When bringing a new partner into the situation prior to a final divorce, especially when one or both partners has children from a previous relationship, documentation becomes even more crucial.