The act of filing for divorce is not exactly known for prompting reconciliation between couples, but that is not to say that it is impossible. A couple from a nearby state made national headlines when they unsuccessfully attempted to undo their divorce. While this is an acceptable option in some states, it is currently not permitted in New York.
When the couple filed for divorce in Jan. 2014, they had been married for 24 years. The grounds on which they filed are not known, although proceedings were finalized in July 2014. Less than a year later, the couple reconciled with one another. Together, they petitioned the court to have their judgment of divorce vacated.
Despite their claim that the divorce settlement should be considered erroneous due to their reconciliation, the original motion to vacate was denied. The couple subsequently appealed and ended up before the New Hampshire Supreme Court, which ruled against the couple. According to the court, the law only granted the the power to grant a divorce, not to undo one.
The same holds true in New York where, aside from extenuating circumstances such as fraud, a divorce cannot be made invalid or overturned. Fortunately, for most couples, this is not a situation that typically arises. While a divorce may not be undone or vacated, it can be amended if necessary. Changes to a settlement are usually granted by the court after one or both parties have filed a petition and provided relevant and necessary evidence for the change. As for undoing a divorce in New York, the parties could simply remarry.
Source: NBC New York, "N.H. Couple Seeking to Undo Their Divorce Gets Turned Down", Lynne Tuohy, Dec. 27, 2015