All employers who are using a pre-approved form for their 401(k), profit sharing, or other defined contribution plan must sign updated documents on or before April 30, 2016 to preserve the tax-qualified status of the plan. 

Most employers who sponsor retirement plans are subject to this requirement.  Read the IRS explanation of why a revised plan is necessary, and what steps employers should take.

Plan vendors have started communicating with employers about this required update.  You should keep an eye out for these communications if you sponsor a retirement plan using a pre-approved form.