What makes a classic? Whether it’s a 1963 Chevrolet Corvette or the Sgt Pepper album, it usually means that it’s the highest in quality, class, or rank. So it’s kind of funny that there are 401(k) plan sponsor mistakes that are actual classics because these mistakes are usually the mistakes that lead a plan sponsor into a whole host of trouble and liability. So this article is about classic 401(k) plan mistakes that you need to avoid in running your plan.