If you plan a simple no fault divorce, involving no children and minimal assets, you may not need a separation agreement. Otherwise, a formal contract setting forth the understandings of the parties concerning divorce and separation is advisable.
A separation agreement does not have to be filed with a divorce court to be enforceable and effective for future divorce purposes. At the time of filing for divorce, it is normal practice in most jurisdictions for a legal divorce and separation process to attach the separation agreement to the complaint or petition initiating the divorce. At the end of the divorce process, the separation agreement can either be merged or incorporated into the final divorce decree. If the separation agreement is incorporated into the divorce decree, the court takes jurisdiction over the details of the separation agreement and can enforce one or more of the separation agreement’s terms through the court’s contempt powers.

If the separation agreement is not incorporated into the divorce decree, it is deemed to be merged into the divorce decree but remains a stand alone contract between the parties which is enforceable only through a separate court action. If there is a violation of an unincorporated separation agreement, an action for money damages can be started. It is cheaper and faster, however, to deal with violations of a separation agreement incorporated into a final divorce decree in a divorce court rather than as a separate civil matter.

A separation agreement is binding for the term of the agreement but can be amended by the parties if both parties agree. A separation agreement can provide that it cannot be modified by a divorce court, unless the issue involves minor children.