There are many incorrect answers to this question floating around…
In most cases, the answer is yes. The Daughters of the American Revolution and Sons of the American Revolution prefer that you use someone who is already on file. It’s simply for ease of verification, as it gives the verifying genealogist less to review. They will allow you to add someone new as long as you can document that person to meet their standards.
There are some societies that believe they’ve identified all qualifying ancestors. If you want to add a new ancestor to one of those society’s rolls, be sure you can thoroughly document that the person meets their standards. Otherwise, focus on connecting to an identified ancestor.