The general rule is that safe harbor 401(k) plans may not be amended mid-year with very limited exceptions.  This rule is one that often frustrates plan sponsors and is one that the IRS has recently said it is taking under consideration.  While the general rule still holds true, the IRS recently published guidance stating that plans will not lose their safe harbor 401(k) status “merely because the plan sponsor adopts a mid-year amendment pursuant to Q&A-8 of Notice 2014-19. Q&A-8 of Notice 2014-19 requires plans to adopt any necessary amendments to comply with Windsor by the later of the last day of the current plan year or December 31, 2014. Without this relief, plan sponsors would have to worry about either not complying with Notice 2014-19 or losing safe harbor status. Thank you IRS for allowing plans to comply with two of your requirements at once.