S-3 vs S-8: Capital-Raising Shelf or Employee Stock Plan Registration

The short version

An S-3 is the registration a company uses to sell securities to investors for cash. An S-8 registers shares the company pays to its own people as compensation. Both add shares to the count over time, but they arrive through different doors, at different speeds and in different sizes.

The Form S-3 is usually a shelf registration: register a dollar amount now, sell pieces of it later. The S-8 registers a number of shares tied to a named plan, such as a stock option or restricted stock unit plan, and those shares reach the market only as awards vest or options are exercised.

Who can use Form S-8

General Instruction A.1 of Form S-8 sets the registrant test. The company must be subject to Exchange Act reporting immediately before filing, must have filed all reports required during the preceding 12 months, and must not be a shell company. A company that was a shell must have stopped being one, and filed current Form 10 information, at least 60 calendar days earlier.

The securities must be offered under an employee benefit plan, defined in Rule 405 as a written purchase, savings, option, bonus, appreciation, profit sharing, thrift, incentive, pension or similar plan, or a written compensation contract, for employees, directors, officers, and consultants or advisors.

Consultants and advisors qualify only if all three conditions in General Instruction A.1(a)(1) hold: they are natural persons, they provide bona fide services, and those services are not connected with the offer or sale of securities in a capital-raising transaction and do not directly or indirectly promote or maintain a market for the company's securities. That last clause is why an S-8 cannot be used to pay a stock promoter or a finder.

Who can use Form S-3

General Instruction I.A of Form S-3 sets the registrant requirements: among them, the company has been reporting under Section 12 or 15(d) for at least 12 calendar months and has filed all required reports in a timely manner during that period, with a short list of 8-K items excepted.

The transaction requirements then decide how much it can sell. Under General Instruction I.B.1, a company whose common equity held by non-affiliates is worth $75 million or more can make primary offerings without a size cap. Below that, I.B.6 allows primary sales of up to one-third of public float in any 12 months. That cap, the baby shelf rule, is covered in S-1 vs S-3 and the baby shelf.

Rule 415(a)(1)(x) lets S-3 securities be sold on a continuous or delayed basis, and Rule 415(a)(5) limits sales off that kind of shelf to three years from its initial effective date.

Speed: why an S-8 is effective the day it is filed

General Instruction D of Form S-8 states that the registration statement becomes effective automatically upon filing, and Rule 462(a) says the same. Delaying amendments are not permitted. On EDGAR, an S-8's header usually shows an effectiveness date equal to its filing date.

A typical S-3 does not work that way. The company files it, may amend it, and sales can begin only after the SEC declares it effective, which shows up on EDGAR as an EFFECT notice. The exception is an automatic shelf filed by a well-known seasoned issuer, which becomes effective immediately under Rule 462(e). Most small caps are not well-known seasoned issuers.

Once an S-3 shelf is effective, nothing has been sold. Each sale is described in a prospectus supplement, usually a 424B5; reading a 424B5 walks through one, and ATM offerings covers the at-the-market version.

One company, both forms

Aeluma (ALMU), filed both forms within about 14 months.

The S-3 stated non-affiliate common equity of $331,915,865 as of July 31, 2025, well above the $75 million I.B.1 threshold.

The S-8 shares came from an "evergreen" clause, which adds shares to the plan each January 1:

From the filing

Form S-8

“the maximum number of shares of Common Stock that may be delivered under the Plan automatically increases by an additional number of shares equal to the lesser of (x) 5% of the outstanding shares of Common Stock (on a fully-diluted basis) on the immediately preceding December 31”

The two numbers are not the same kind of dilution. The 1,700,000 offering shares were sold and outstanding on closing. The 2,686,517 S-8 shares are a ceiling on what the plan can deliver; they become outstanding only as awards are granted and then vest or are exercised, which can take years. The 13.94% figure is the maximum the registration allows, not a measure of shares issued.

Selling S-8 shares after they are issued

Shares issued under an S-8 to a non-affiliate are generally freely tradeable. Affiliates, meaning officers, directors and controlling holders, are treated differently. General Instruction C allows a separate reoffer prospectus filed with the S-8 for control securities and restricted securities acquired under the plan. If the company does not meet the S-3 registrant requirements, resales through that prospectus are limited in any three months to the amount in Rule 144(e).

A reoffer prospectus names the selling holders, or adds them later by supplement. Their actual sales still appear on Form 4; see Form 4 vs Form 144.

What to watch for

• An S-8 for a large share count relative to shares outstanding.
• S-8 shares issued to consultants. The form's conditions exclude capital-raising and market-promotion services, so the plan document and the consultant's role are worth reading.
• An S-3 with no 424B5 yet. That is capacity, not dilution. What is dilution? covers how registered capacity differs from shares issued.
• Loss of S-3 eligibility. A late periodic report can push a company to a longer S-1 for new offerings; see Form S-1 explained.

How to check a company on Signal8

• The live SEC filings feed shows S-3, S-8 and 424B5 filings as EDGAR accepts them.
• A company's filings tab, for example ALMU's filings, lists its registration statements and prospectus supplements together.
• The Dilution tab on a company page collects dilution-related data where Signal8 has measured it.
• The dilution screener lets you compare companies on dilution-related data.

The form texts are on SEC.gov: Form S-3 and Form S-8. The rules are on eCFR: Rule 405, Rule 415 and Rule 462.

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