What Is an ATM Offering? Definition and How to Read It in SEC Filings

Direct answer: An ATM offering (At-The-Market offering) is a share sales program that authorizes a public company to issue and sell newly created shares directly into the open market, at prevailing market prices, gradually and with no fixed amount. The company turns sales on or off according to its cash needs, diluting existing shareholders a bit at a time. Small-caps favor the mechanism for its flexibility and its lower fees compared with a traditional public offering.

How an ATM offering works

An ATM offering (At-The-Market offering, sometimes called an "at-the-market sales program") lets a public company sell newly issued shares directly into the secondary market, at the live market price, rather than through a traditional fixed-price public offering.

In practice, the company appoints a sales agent — usually an investment bank — that sells the shares into the market over time, in small lots, to limit the impact on the price. The program sets a ceiling (for example "up to $100 million of common stock"), but management decides when to turn sales on or off, and at what pace.

Unlike a traditional capital raise (follow-on offering), where the company raises a fixed amount all at once at a negotiated price, an ATM commits to no amount and no schedule: it is a financing tap the company opens or closes according to its cash needs and market conditions. Commissions are also lower — generally 2% to 3% of gross proceeds, versus 5% to 7% for a traditional public offering, based on observed market data.

Where to read about an ATM offering in SEC filings

An ATM offering is documented across several public SEC filings, available free of charge on SEC EDGAR:

Initial prospectus and supplements (Form S-3)

An ATM program is generally established through a Form S-3 (registration statement) and a specific prospectus supplement that describe:

• The maximum amount of shares that can be sold (in dollars or in number of shares)
• The designated sales agent
• Commissions and fees
• The selling mechanics (primary market, sold over time)

The prospectus supplement is filed as a 424B5 or 424B2 on EDGAR, and refers back to the underlying shelf registration statement (Form S-3).

Quarterly and annual reports (10-Q, 10-K)

The quarterly (Form 10-Q) and annual (Form 10-K) reports detail how the ATM was actually used:

• Number of shares sold during the period
• Gross and net proceeds received (after commissions)
• Weighted average sale price
• Remaining balance available under the program (in dollars)

This information typically appears in the "Liquidity and Capital Resources" or "Stockholders' Equity" sections of the notes to the financial statements.

Current reports (Form 8-K)

A Form 8-K (current report) may be filed when the ATM is first launched, when the program is materially amended (ceiling increased, sales agent changed), or sometimes after large sales under the program. Some companies file an 8-K each time a sales threshold is crossed — for example every 10% of the program used.

Why small-caps favor ATM offerings

ATM offerings show up frequently among small-caps and biotechs, for several structural reasons documented in the SEC filings:

Maximum flexibility. Management can turn the ATM on while the price is high — after positive clinical-phase news or a commercial contract, for instance — and pause sales if the market falls. That optionality shapes the price at which dilution happens, unlike a traditional public offering, which has to be executed at one point in time whatever the price.

Lower cost. ATM commissions (typically 2% to 3% based on observed prospectuses) are generally below those of a traditional public offering (generally 5% to 7%), and legal and administrative costs are lower too, since the shelf registration statement (S-3) can serve several successive programs or tranches.

No immediate market pressure. A traditional public offering places a large block of shares all at once, which mechanically creates selling pressure and often pushes the price down. An ATM, selling gradually and in small lots, dilutes quietly without a liquidity shock.

Funding a cash burn over time. Development-stage companies (biotech, cleantech, early-stage SaaS) have a continuous and unpredictable cash burn. An ATM funds that burn quarter by quarter, raising exactly what is needed, without over-raising — and therefore over-diluting — the way a fixed raise would.

The impact on float and dilution

Every share sold under an ATM is newly issued, so it raises shares outstanding and, in turn, the float, mechanically diluting existing shareholders. How large the dilution gets depends on three factors:

Factor	Impact on dilution
Volume sold	More shares sold = heavier dilution
Average sale price	Lower price = more shares issued for the same amount raised
Initial float	Small initial float = heavier proportional dilution

Mechanical example (arithmetic illustration, not a recommendation): a company with 20 million shares outstanding turns on a $50 million ATM. If the average sale price is $5 per share, the ATM will issue 10 million new shares ($50M ÷ $5), bringing the total to 30 million shares. Mechanical dilution is then 33% (10M / 30M). If the average price drops to $2.50, the same ATM will issue 20 million shares, for mechanical dilution of 50% (20M / 40M).

So there are two metrics to watch in the quarterly reports:

• The remaining balance available under the ATM program (indicates potential future dilution)
• The weighted average sale price of the shares already sold (indicates the timing of the sales)

An ATM used heavily at low prices generally signals urgent cash needs; an ATM used selectively at high prices often reflects opportunistic financial management.

Variants and special cases

The "controlled equity offering" ATM

Some companies run an ATM as a controlled equity offering (CEO), a Cantor Fitzgerald trademark. The mechanism is identical — selling into the market over time — but the sales agent provides additional advisory services and an online management platform to track sales in real time.

ATM "sales agreement" vs "underwritten offering"

An ATM is always a sales agreement: the agent acts as an agent, not as an underwriter. There is no placement guarantee and no risk taken by the bank, unlike an underwritten offering, where the banks buy the shares and then resell them into the market, taking market risk in the process.

Regulatory limits

An ATM can only sell shares already registered under a valid shelf registration statement (Form S-3). A company has to meet certain conditions to be S-3 eligible, notably a minimum public float or a history of regular SEC filings. Micro-caps that recently went public sometimes use a Form S-1 instead, but the ATM mechanism stays the same.

Recap

Point	Takeaway
Definition	A share sales program at prevailing market prices, over time, with no fixed amount and no fixed schedule
Trigger	Management turns sales on or off according to cash needs and the share price
Dilution	Every sale raises shares outstanding and the float, diluting existing shareholders proportionally
Where to read it	Form S-3 and prospectus supplement (the program), 10-Q and 10-K (actual usage), sometimes 8-K
Advantages for the company	Flexibility, lower cost, no immediate market pressure, funding the cash burn over time
Impact for the shareholder	Continuous and unpredictable dilution, particularly significant if the ATM is used heavily at low prices

FAQ

What is an ATM offering in the stock market?

An ATM offering (At-The-Market offering) is a share sales program that authorizes a public company to issue and sell newly created shares directly into the open market, at prevailing market prices, gradually. The company can turn sales on or off according to its cash needs, with no fixed amount and no fixed schedule. The mechanism dilutes existing shareholders a bit at a time, unlike a traditional one-shot capital raise.

Where do I find information about an ATM offering in SEC filings?

An ATM offering is documented across several SEC filings: the initial prospectus (Form S-3 and prospectus supplement), which describes the program, its maximum size and the sales agent; the quarterly (Form 10-Q) and annual (Form 10-K) reports, which detail the number of shares sold, the net proceeds received and the remaining balance available; and sometimes a Form 8-K when the program is launched or materially amended. These documents are available free of charge on SEC EDGAR.

Why do small-caps use ATM offerings?

Small-caps favor ATM offerings for their flexibility and lower cost. An ATM lets a company raise money a bit at a time with no committed amount and no steep underwriting fees, which suits financing a cash burn without diluting heavily all at once. Clinical-stage or high-growth companies often turn the ATM on while the price is high, then pause sales if the market falls, which shapes the price at which dilution happens.

What is the difference between an ATM offering and a traditional public offering?

A traditional public offering (follow-on offering) raises a fixed amount of shares at a fixed price negotiated with underwriters, all at once, with high placement fees (generally 5% to 7%). An ATM offering instead authorizes gradual sales at prevailing market prices, with no fixed amount and no fixed schedule, lower commissions (often 2% to 3%) and no volume commitment. An ATM gives management more control and dilutes a bit at a time instead of in a single shock.

How does an ATM offering affect float and dilution?

Every share sold under an ATM is newly issued, so it raises shares outstanding and, in turn, the float, mechanically diluting existing shareholders. The impact depends on the volume sold and the sale price: a $50 million ATM sold at $5 adds 10 million shares, which can represent 10% to 30% dilution depending on the initial float. The quarterly reports (10-Q) let you track cumulative dilution and the remaining balance available under the program.

Sources

• SEC EDGAR (search filings by ticker)
• Form S-3 (shelf registration statement) – registration of securities for delayed sale
• Form 10-Q – quarterly reports with the detail of ATM usage
• Form 10-K – annual reports with the dilution picture
• Form 8-K – current reports for material events
• SEC – Regulation S-K – disclosure requirements on equity and dilution

See the float, sourced and dated, on FloatVerify.

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FloatVerify shows the float, dilution and cash burn of US small-caps, every number sourced and dated — and surfaces divergences between sources ("source split") instead of one falsely certain figure.

Disclaimer: FloatVerify is a data tool, not an investment advisory service. Nothing here is a recommendation to buy or sell. Data, not advice.