Separation means living in two different residences, with the intent on the part of at least one of the spouses that the separation be permanent.  You cannot live in the same house and be separated.  Living in separate rooms of the same house does not constitute a separation.

On the other hand, you do not need a document to be separated for the purpose of divorce.  You are separated when you begin living in two different residences with at least one spouse intending that separation to be permanent.  There are a great many other areas or endeavors for which a separation agreement will be beneficial, or even necessary.  But, not for the purpose of getting a divorce and/or for filing claims for child custody, child support, alimony and other family law related matters. 

A lawyer cannot allow you to “back-date” your separation to a date prior to the day that one of you actually moved out (even if the other party agrees to it), nor are you allowed to do so yourself if you act as your own lawyer.  Attempting to do this can be a criminal offense.  Just don’t do it.

Most of the time, either the parties agree to separate or one party decides to move out.  If both parties are dug in and refuse to leave the marital home, then the options to start a separation are limited.  Divorce from Bed and Board is one option, but it is far from ideal.  These options require a more in-depth discussion about the facts and circumstances in your case in an in-office consultation