Buffett's 2021 letter to shareholders also includes some mea culpas explaining why operating earnings fell last year and shares underperformed.

The IRS guidance addresses retirement plan participants "who are due a benefit but cannot be located," Slott says.

Workers with dual participation are likelier to take advantage of financial advice, Fidelity research shows.

Insights from the Brightscope/Investment Company Institute (ICI) survey on DC retirement plans.