This is the most important point. ALWAYS. These plans are subject to a host of IRS (and in case of ERISA plans, DOL) rules. This goes far beyond delivering beautiful reports that will never be requested by the IRS (or DOL) during audit. In many instances, clients are inundated with reports while failing to meet regulatory requirements during audit. So, you have to align with a service provider to knows what is required and constantly keep you in compliance with respect to those standards. So, in this example, who is responsible for determining if, of when, filing is necessary is one of potentially unlimited issues that should be considered.