Divorcing couples are usually most concerned with the date their divorce will become final, but there are a number of reasons why the "date of separation" (when one spouse decides the marriage is officially over) is actually more important. Courts in many states use the date of separation as an important factor in deciding issues related to property division, child support, alimony and adultery.
The specific definition of the "date of separation" varies from state to state, but it's usually considered the date that spouses no longer live together as a married couple. However, some of these definitions don't necessarily require living in different residences. In California, for instance, the date of separation means the date when there's been "a complete and final break in the marital relationship." To show that has happened, one spouse must have communicated to the other spouse an intent to end the marriage and must have acted in a way that's consistent with that intention. (Cal. Fam. Code § 70 (2022).)
When spouses don't immediate move out even though they plan to end the relationship, judges may look at other circumstances to determine the date of separation, such as when a spouse moved into a separate room in the house or filed for divorce.
Similarly, when one spouse moves out but hasn't decided to get divorced, the judge will look for other evidence of when the couple actually intended to split, such as the date a spouse hires an attorney, communicates to the other spouse an intent to divorce, or actually files for divorce.
In most states, any income spouses earn during the marriage is considered marital property (or "community property" in a few states), unless they have a valid prenuptial agreement that says otherwise. You might think that "during the marriage" means before the divorce is final, but that's not true in all states. For the purpose of this rule on marital property, some states use the separation date as the cutoff, while some other states use the date when a spouse started the divorce process or when the court issued the final divorce decree.
In states that use the separation date as the cutoff, income spouses earn after that date will be their separate property. What's important here is when the income was earned, not when it was paid. So, for example, if a couple separates halfway through the year, the judge may decide that half of one spouse's year-end bonus is marital property. With stock options or other types of deferred payment, judges typically use the specific circumstances to value the asset as of the date of separation.
As with income, other types of property acquired during the marriage will also be considered marital or community property, with a few exceptions (such as gifts and inheritances).
The date of separation can determine when a spouse becomes responsible for child support and/or alimony (also called "spousal support"). For example, if a husband who earns all of the household income moved out of the marital residence, a judge might order him to pay temporary child support and alimony from the date he left. In some states, however, a spouse may only be eligible for child support or alimony after filing for divorce and asking for support. It's important to speak with an attorney soon after your date of separation to ensure you're eligible to get the support you deserve.
Although all states allow you to file for a no-fault divorce, many states still allow you to get a divorce based on your spouse's adultery. And in some states, a spouse's adultery may affect how the judge decides certain issues in the divorce, especially alimony. For these purposes, however, many states won't consider it to be adultery when someone starts a new sexual relationship after separating from their spouse.