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Compare · Paying for advice · Updated 2 September 2026

Fiduciary vs best interest vs suitability

Three standards that sound similar and permit different things. The difference is mostly about when the duty attaches.

The short answer

A fiduciary duty binds a registered investment adviser continuously, across the whole relationship, with duties of care and loyalty. Regulation Best Interest binds a broker-dealer at the moment of a recommendation to a retail customer — a real standard, but a narrower one, and it does not require the lowest-cost option. Suitability, the older standard, asks only that a recommendation fit the customer. You can check which one applies to any firm in about two minutes at adviserinfo.sec.gov, for free.

Three standards, and what each one permits

Fiduciary dutyRegulation Best InterestSuitability
Who is held to itRegistered investment advisersBroker-dealers, when recommending to retail customersThe older broker-dealer standard, largely superseded by Reg BI in 2020
The dutyAct in the client's best interest at all times, with duties of care and loyaltyAct in the retail customer's best interest at the time of a recommendationRecommend something suitable for the customer
When it appliesContinuously, across the relationshipAt the moment of a recommendationAt the moment of a recommendation
Conflicts of interestMust be eliminated or fully disclosedMust be identified and disclosed, and some mitigatedDisclosure obligations narrower
Can a more expensive product be recommended?Only if it is genuinely better for youCost must be considered, but the cheapest is not requiredYes, if suitable
SourceAdvisers Act §§206; SEC v. Capital Gains (1963)SEC Rule 15l-1 (2020)FINRA Rule 2111

The distinction that matters most is not the wording of the duty but when it attaches. A fiduciary duty runs continuously; Regulation Best Interest attaches to a recommendation. Between recommendations, the obligation is thinner.

California adds a layer, and it is stricter

Aduna Capital is registered with the California Department of Financial Protection and Innovation rather than the SEC, so state rules apply on top of the federal ones. California Code of Regulations title 10, section 260.238 sets out conduct that fails the “fair, equitable and ethical principles” standard, and section 260.235 governs advertising — including an outright ban on client testimonials for state-registered advisers, with no disclosure that cures it. That is why there are no reviews or client quotes anywhere on this site, and why any firm in California displaying them is either SEC-registered or has a problem. Our fiduciary commitment, in writing →

How to check, in two minutes, for free

  1. Go to adviserinfo.sec.gov and search the firm or the person.
  2. If the record says investment adviser, a fiduciary duty applies. If it says broker, Regulation Best Interest applies. Many people are registered as both, which means the applicable standard depends on which hat they are wearing at the time — and you are entitled to ask which one, in writing.
  3. Open Form ADV Part 2A. Item 5 is compensation. Item 10 is other business activities. Item 14 is payments for client referrals. Read those three.
  4. Check the Disclosures tab for regulatory events, complaints and settlements.

Two minutes there tells you more than an hour of any firm’s marketing, ours included. Aduna Capital’s record is here — CRD #311270.

Words that are not the same as the duty

  • “Trusted adviser”, “we put clients first”, “client-focused” — marketing, not a legal standard. Anyone may say them.
  • “Financial adviser” and “financial consultant” — titles, not registrations. The registration is what carries the duty.
  • “Fee-based” — not fee-only. It usually means fees plus commissions. The difference matters →
  • “Independent” — describes the firm’s ownership, not how it is paid.

Common questions

Are all financial advisers fiduciaries?

No. Registered investment advisers owe a fiduciary duty. Broker-dealers are held to Regulation Best Interest, which applies at the point of a recommendation rather than continuously. Insurance agents selling insurance products are generally subject to neither, though some states impose a best-interest standard on annuity sales.

Is Regulation Best Interest the same as a fiduciary duty?

No, and the SEC said so when it adopted the rule. It is a meaningful improvement on the old suitability standard, but it attaches to recommendations rather than to the relationship, and it does not require the lowest-cost option.

Can someone be a fiduciary only some of the time?

Yes, and it is common. A person registered as both an adviser and a broker owes a fiduciary duty in the advisory relationship and a different standard on brokerage business. Ask which capacity applies to the specific recommendation, and ask in writing.

Is Aduna Capital a fiduciary?

Yes, at all times, in writing, in every client relationship — and we are fee-only, so clients are our only source of revenue. What that commits us to →

This guide is general education, not individualised investment, legal or tax advice, and reading it does not create an advisory relationship. Individual circumstances vary — figures, limits and rules cited here change over time and may not apply to your situation. Confirm current figures with the IRS, the Social Security Administration, or your plan documents, and consider speaking with a qualified adviser or CPA before acting. Aduna Capital LLC is a California DFPI-registered investment adviser (CRD #311270). Aduna Capital LLC is not affiliated with, endorsed by, or sponsored by CalSavers, the California State Treasurer's Office, CalPERS, CalSTRS, or any other retirement system, employer or school district named on this page.

See our record before you call

CRD #311270, public, free, no login. Then take fifteen minutes with us if you like what you read.