An at-the-market (ATM) offering lets a public company sell new shares gradually into the open market, at whatever the stock is trading for, through a broker acting as its sales agent. For traders, it means a company can add share supply on any trading day without announcing each sale, so the size of the program and how much of it is left both matter.
This guide covers how ATMs work, why small caps rely on them, how to read an ATM filing, and how to check a company's remaining ATM capacity in Ask Edgar.
How an ATM offering works
An ATM is a registered offering, so it sits on top of a shelf registration. The usual sequence looks like this:
- The company files a shelf registration, typically on Form S-3. Once the SEC declares it effective, the company can sell securities from it over time.
- The company signs a sales agreement with a broker-dealer, often called an equity distribution or at-the-market agreement. The broker acts as its sales agent.
- The company files a prospectus supplement, usually on Form 424B5, that sets the maximum dollar amount it can sell under the ATM.
- The agent sells shares into the market from time to time, at prevailing prices, as the company directs. The agent earns a commission on what it sells.
There's no single pricing event, no fixed share count and no discount negotiated with a buyer. Shares go out in small amounts over days, weeks or months. The company doesn't announce each sale, so you find out what it sold from its later SEC filings.
Why small caps use ATMs
For a company that needs cash regularly, an ATM is one of the most flexible ways to raise it.
- Timing: the company can sell when volume and price are favorable, and pause when they aren't.
- Cost: there's usually no underwriting discount or deal-sized marketing effort, just the agent's commission.
- Pricing: shares sell at market prices instead of at the discount a one-off offering often needs.
- Size: the company only raises what it needs, when it needs it, up to the program's limit.
That flexibility is why companies with short cash runways often keep an ATM in place, even when they aren't actively selling.
What an ATM means for traders
An active ATM is a source of steady selling. Because the agent sells into whatever demand shows up, a rally or a spike in volume can be exactly when the company chooses to sell. That can cap a move or make it fade faster than the chart alone suggests.
An ATM doesn't mean shares are being sold today. A company can leave a program unused for months. What matters is:
- How much capacity is left. A $50 million program with $2 million remaining is a very different overhang from one that's barely been touched.
- How much cash the company needs. A short runway makes it more likely the company will use the ATM.
- What the company has already sold. Later SEC filings show whether the company has been using the ATM. For baby shelf companies, each new prospectus cover must state how much was sold under the rule in the past 12 months.
None of this predicts a price move on its own. It tells you where extra supply could come from, so you can weigh it alongside the rest of your research.
How to read an ATM filing
The prospectus supplement for an ATM, usually a 424B5, answers most of the questions above. Look for:
- The aggregate offering amount: the most the company can sell under this program.
- The sales agent: the broker-dealer handling the sales.
- The shelf it's filed under: the supplement references the shelf registration's file number, which tells you which shelf it draws from.
- The baby shelf limit, if it applies: companies with a public float under $75 million are generally limited by Form S-3's baby shelf rule to selling no more than one-third of their public float in any 12-month period. The limit is measured using a share price from the 60 days before a sale, and companies typically pick the highest closing price in that window. The supplement's cover must show the public float calculation and how much the company has sold under the limit in the past 12 months.
The baby shelf rule is why a small company's ATM size can look strange. A company may register a large shelf but only be able to sell a fraction of it each year. As its share price or float grows, the amount it can sell grows too, and the company often files a new or amended supplement to raise the ATM size.
A real example: Datavault AI (DVLT)
Here's how an ATM looks in Ask Edgar's registration data for Datavault AI, as last updated on 24 October 2026:
- The shelf: a $250 million shelf filed on 7 July 2025 under file number 333-288538.
- The ATM: a $50 million ATM filed on 22 July 2025, with Maxim Group LLC as sales agent, under the same file number. The shared number shows the ATM draws on that shelf.
- What's left: Ask Edgar shows $13.8 million of ATM capacity remaining. The offering-risk rating for DVLT reports the same $13.8 million.
That last figure is the one to watch. The $50 million headline was the program's starting size, not what the company can still sell.
Check ATM capacity with the API
The registrations endpoint returns a ticker's shelves, ATMs and resale registrations. Request it with your API key in the API-KEY header; the quickstart shows how. The fields that matter for ATMs:
- is_atm: true for ATM programs.
- offering_amount: the program's registered size.
- amount_remaining_atm: the capacity Ask Edgar reports as remaining.
- bank: the sales agent.
- file_no: the registration file number, which links an ATM to its shelf.
- filed_at and document_url: when it was filed, and a link to the filing on SEC EDGAR.
Results come 10 to a page, so follow has_more to get every registration. Check the cost first with the free estimate endpoint: https://eapi.askedgar.io/estimate?endpoint=registrations&ticker=DVLT
Common questions
Is an ATM offering bad for a stock? Not automatically. It adds potential supply, and heavy use can weigh on the price. It also funds the company's operations, which can matter more than the dilution. Read it alongside the company's cash position.
Does a new ATM mean the company is selling right now? No. It means the company can sell. Check its later SEC filings for how much it has actually sold.
What's the difference between a shelf and an ATM? A shelf registration lets a company sell securities over time. An ATM is one way of selling from that shelf, gradually into the market. A company can also use the same shelf for other offerings, such as a registered direct offering.
How is an ATM different from a registered direct offering? A registered direct offering sells a fixed block of shares to specific investors at a set price, usually announced all at once. An ATM sells small amounts into the open market over time at market prices.
Why would a company with a large shelf have a small ATM? Often because of the baby shelf limit. A company with a public float under $75 million can generally sell only one-third of its public float in a 12-month period, however large its shelf is.
Start building
Look up any ticker's ATM and shelf capacity in the Ask Edgar app. If you're building your own screener or watchlist, get an API key and add credits, then follow the quickstart to pull registration data.
Last checked against Ask Edgar data on 25 October 2026.