This waiting period serves the purpose of allowing parties to change their mind before the divorce becomes final. If the Judgment of Divorce Nisi has issued but not become final yet, and you and your spouse decide you don't want to get divorced, then you can file a Motion to Dismiss and the Judgment will be undone. Although many of my clients who are getting divorced think the idea of getting back together with their ex sounds crazy, I have had cases where this happened.
In addition to offering a grace period to change your mind, the Nisi period has three other legal effects:
1. The most obvious effect of the waiting period is that you cannot remarry during the Nisi period, because you would then technically be married to two people.
2. If the Nisi period crosses December 31, then you are considered married for that tax year which means you must file under "joint" or "married, filing separately" and cannot file as "single".
3. Under some health insurance plans you may not be able to stay on your ex's health insurance (as explained further in our previous post, Will I be able to keep my health insurance after the divorce?), but at least during the Nisi period you can stay on the health insurance.