ERISA 3(21) vs. 3(38) Investment Fiduciary: What's the Difference?
When a retirement plan brings in outside help to manage its investment lineup, the letters attached to that relationship can matter as much as the advice itself. Two designations under federal pension law describe very different levels of authority, and confusing them can leave a plan sponsor unsure of who is actually making the calls.
The short answer
Under ERISA, a 3(21) fiduciary offers investment recommendations that the plan sponsor can accept, modify, or reject, while a 3(38) fiduciary is granted full discretionary authority to select and change investments on its own. The core difference is who has the final say and who carries legal responsibility for that specific decision. Choosing between them changes how much oversight work a sponsor retains, though it doesn’t erase the sponsor’s broader duties.
How a 3(21) relationship works
A 3(21) investment advisor operates as a co-fiduciary. It studies the plan’s fund lineup, benchmarks costs and performance, and delivers recommendations in writing, but the plan sponsor — often a business owner or a committee of employees — makes the actual decision to add, remove, or keep a given fund. Because the sponsor retains that final signature, it also retains a share of the liability if a recommendation turns out to be a poor fit or goes unexamined for too long. The advisor is accountable for the quality of the advice given, not for whether the sponsor acted on it wisely.
How a 3(38) relationship shifts the picture
A 3(38) fiduciary is different in kind, not just degree. It receives contractual, discretionary authority over some or all of the plan’s investment menu, meaning it can add, remove, and replace funds without routing each change back to the sponsor for approval. This can meaningfully reduce the sponsor’s exposure to claims specifically about fund selection and monitoring, since that task has been delegated to a professional bound by the same fiduciary standard. It doesn’t, however, remove the sponsor’s ongoing duty to monitor whether the 3(38) itself is doing a competent job — delegation shifts one layer of responsibility, not all of it.
Why smaller plans weigh this differently
Employers running a plan without a dedicated benefits or investment staff often find the 3(38) structure appealing precisely because it removes a task few small business owners are equipped to perform well: continually evaluating expense ratios, share classes, and fund performance against appropriate benchmarks. Larger organizations with an internal retirement committee sometimes prefer the 3(21) model instead, since it keeps ultimate investment authority in-house while still benefiting from professional input. Cost structures for the two services can also differ, and that’s worth factoring in alongside the liability question.
What the choice does and doesn’t solve
It’s worth being clear-eyed about what either arrangement accomplishes. Neither designation is a shortcut around selecting a qualified financial advisor in the first place, and neither eliminates the sponsor’s broader fiduciary duty to act prudently and solely in participants’ interest. Plans that treat either arrangement as a “set it and forget it” solution are the ones most likely to end up facing scrutiny — a pattern that shows up in the allegations behind many excessive fee disputes brought against plan sponsors over the years.
The takeaway
The 3(21) versus 3(38) distinction is really a question of where a specific decision-making authority sits and who answers for it. A 3(21) advisor informs; a 3(38) advisor decides. Either structure can work well when it’s paired with genuine oversight, documentation, and periodic review — the parts of the fiduciary role that never get fully delegated away.