The suitability standard and the fiduciary standard are two very different rules for the same conversation. The suitability rule, used for decades by FINRA-registered brokers, said a broker had to recommend products that were not unsuitable for the client. The 2020 Reg BI rule replaced suitability with a slightly stronger standard called "Best Interest," but the bones are similar. Under both, a broker can recommend a more expensive product over a cheaper one, as long as the more expensive one is not clearly bad for you. Under the fiduciary rule, used by Registered Investment Advisers, the firm has to recommend the option that is best for you, full stop. The duty also covers ongoing care, conflict disclosure, and a duty of loyalty. The difference shows up in real money. A 0.50% fund vs. a 1.50% fund can both be suitable. Only one is in your best interest.
The plain-English version
| Suitability / Reg BI | Fiduciary | |
|---|---|---|
| Who follows it | Brokers, dual-registered reps | RIAs and IARs |
| What they must do | Pick something not unsuitable | Pick what is best for you |
| Conflicts | Disclose at sale | Disclose, manage, or avoid |
| Ongoing duty | At the time of recommendation | Continuous |
| Enforced by | FINRA, SEC | SEC, state regulators |
A worked example
You walk into a broker's office with $500,000 to invest. The broker recommends a Class A mutual fund with a 4.75% front-end load and a 0.85% expense ratio. They earn the load as a one-time commission, plus a 12b-1 trail. Under suitability, the recommendation is fine because the fund is "not unsuitable": the asset mix is reasonable for your age. Under fiduciary, the recommendation is a problem. A no-load index fund with a 0.05% expense ratio is the same asset mix at one-tenth the cost. A fiduciary has to recommend the cheaper one.
Why the difference matters
The whole reason fee-only fiduciary advice exists is to remove the gap between "not unsuitable" and "best." A fee-only RIA cannot earn a load. There is no one to pay them but you. So the cheaper, better fund wins by default.
A quick test for your own setup
Pull your most recent statement and look at the funds in your account. Note the ticker for each. Look up each ticker on Morningstar.com and check the expense ratio. If most of your funds are in the top half by cost (over 0.50% expense ratio), your advisor's recommendations may have cleared "suitability" but not "fiduciary." The math is the same whether the rule is "suitable" or "best." The rule changes who that math is allowed to favor.
