# Mainstreet RIA LLC

> Mainstreet RIA LLC is an SEC-registered investment advisory firm in O'Fallon, MO, registered since 2021, reporting $100 million to $500 million in regulatory assets under management in its Form ADV filing dated September 29, 2026.

- CRD: 309150
- Filed as: MAINSTREET RIA LLC
- Registration: SEC-registered investment adviser (status as filed: Approved)
- Location: O'Fallon, MO
- Filing period: October 2026
- Form ADV filing dated: September 29, 2026
- SEC record (IAPD): https://adviserinfo.sec.gov/firm/summary/309150
- AdvisorCensus page: https://advisorcensus.com/firm/mainstreet-ria-llc-o-fallon-mo-309150

## Quick answers

**How is Mainstreet RIA LLC compensated?**
On its Form ADV (Item 5.E, October 2026), Mainstreet RIA LLC reports these compensation arrangements: a percentage of assets under its management; hourly charges; fixed fees (other than subscription fees).

**Where is Mainstreet RIA LLC located?**
Mainstreet RIA LLC's principal office is in O'Fallon, MO, according to its Form ADV.

**Is Mainstreet RIA LLC registered with the SEC or a state?**
Mainstreet RIA LLC is an SEC-registered investment advisory firm, registered since 2021. Status as filed: Approved. CRD 309150.

**How much does Mainstreet RIA LLC manage?**
Mainstreet RIA LLC reports $471,751,580 in regulatory assets under management in its Form ADV filing dated September 29, 2026 (100% discretionary).

**How have Mainstreet RIA LLC's assets and staff changed since 2021?**
In the Form ADV data for Mainstreet RIA LLC: Regulatory assets under management: $276,500,000 in the October 2021 data and $471,751,580 in the October 2026 data, up 71%. Total employees: 3 in October 2021 and 3 in October 2026. Assets under management move with markets as well as with clients coming and going.

**What types of clients does Mainstreet RIA LLC serve?**
By number of clients on Form ADV Item 5.D: individuals (other than high net worth individuals) (124); high net worth individuals (12); pension and profit sharing plans (but not the plan participants or government pension plans) (5).

**Which custodians does Mainstreet RIA LLC use?**
Mainstreet RIA LLC's most recent Form ADV filing (Schedule D, Section 5.K(3)) lists Charles Schwab & Co., Inc. and Corebridge Retirment Services as custodians holding 10% or more of its separately managed account assets.

**Does Mainstreet RIA LLC report any disciplinary disclosures?**
Reports no disclosure items on Form ADV Item 11. The detail of any item is on the firm's SEC record: https://adviserinfo.sec.gov/firm/summary/309150

**Does Mainstreet RIA LLC state an account minimum?**
Its Form ADV Part 2A brochure dated February 12, 2026 says: "Mainstreet requires a minimum of $ 250,000 to open an account. In certain instances, the minimum account size may be lowered or waived."

**What changed in Mainstreet RIA LLC's recent Form ADV filings?**
In the March 2026 filing data: Regulatory assets under management went from $392,246,687 to $446,355,239 (+14%).

## From the Form ADV filing

### Compensation (Item 5.E)
- A percentage of assets under your management
- Hourly charges
- Fixed fees (other than subscription fees)

### Fees and minimums (Form ADV Part 2A brochure dated February 12, 2026)

- Account minimum: $250,000 (the brochure says it may be waived or negotiated)

> Mainstreet requires a minimum of $ 250,000 to open an account. In certain instances, the minimum account size may be lowered or waived.

As stated in the firm's brochure. Fees can differ by service and may be negotiable.

### Custodians (Schedule D, Section 5.K(3))
- Charles Schwab & Co., Inc.
- Corebridge Retirment Services

Custodians holding 10% or more of the firm's separately managed account assets, as filed on Form ADV (Schedule D, Section 5.K(3)). A custodian holds client assets; it does not endorse or supervise the firm. AdvisorCensus has no relationship with any custodian.

### Regulatory assets under management (Item 5.F)
- Total: $471,751,580
- Discretionary: $471,751,580
- Non-discretionary: $0

### Clients (Item 5.D)

| Client type | Clients | Assets |
| --- | --- | --- |
| Individuals (other than high net worth individuals) | 124 | $47,176,513 |
| High net worth individuals | 12 | $28,712,367 |
| Pension and profit sharing plans (but not the plan participants or government pension plans) | 5 | $395,862,700 |

### Advisory services (Item 5.G)
- Financial planning services
- Portfolio management for individuals and/or small businesses
- Pension consulting services
- Educational seminars/workshops

### Firm details
- Registered since: 2021 (5 years)
- Employees: 3 total, 3 performing advisory functions
- Wrap fee program participation: No
- States registered or notice-filed: IL, MO, TX
- Disclosures (Item 11): Reports no disclosure items on Form ADV Item 11.

### Websites listed on Form ADV (Item 1.I)
- mainstreet-ria.com
- Facebook @Mainstreet-RIA-LLC-106408621387723
- Instagram @mainstreet_ria_llc
- LinkedIn @mainstreet-ria-llc
- TikTok @mainstreet_ria_llc
- YouTube @UCNP_UIkupUMJP7cUDV4hoCw

## Assets and staff over time

| Data period | Regulatory assets under management | Employees | Filing dated |
| --- | --- | --- | --- |
| October 2021 | $276,500,000 | 3 | September 16, 2021 |
| October 2022 | $287,400,000 | 3 | August 30, 2022 |
| October 2023 | $274,296,110 | 3 | January 18, 2023 |
| October 2024 | $374,979,985 | 3 | July 16, 2024 |
| October 2025 | $392,246,687 | 3 | January 15, 2025 |
| October 2026 | $471,751,580 | 3 | September 29, 2026 |

Regulatory assets under management: $276,500,000 in the October 2021 data and $471,751,580 in the October 2026 data, up 71%.
Total employees: 3 in October 2021 and 3 in October 2026.

## Changes in the filing (last 12 months)

### March 2026
- Regulatory assets under management went from $392,246,687 to $446,355,239 (+14%).

## Source

Form ADV as filed, October 2026. Values appear as filed. Cite as: AdvisorCensus. Mainstreet RIA LLC (CRD 309150): Form ADV filing data as of October 2026.