A common stock purchase agreement is the binding contract a corporation uses to sell shares of its common stock to an investor, setting the number of shares, the price, the promises each side is making, and the restrictions that follow the buyer after closing. It is the document behind founder stock issuances, seed rounds, and most early venture financings, and the details inside it decide who owns what percentage of the company, how quickly that ownership becomes yours, when you can sell, and how much you will owe the IRS along the way.
Read it as a package. The signature page is the smallest part of the decision.
What the Agreement Actually Contains
Every stock purchase agreement opens with the basics: the legal names and addresses of the corporation and the purchaser, the number of shares being sold, the price per share, and the total purchase price. The share count has to fit within the company’s authorized shares as set in its corporate charter. A corporation cannot issue more shares than its charter allows, and if the authorized count is too low, the board has to amend the charter before closing the deal.
For early-stage startups, the price per share is often a fraction of a penny, sometimes $0.0001 or $0.01. That low price reflects the company’s minimal fair market value at incorporation. A founder buying 5,000,000 shares at $0.0001 pays $500 for a meaningful ownership stake.
Disclosure schedules travel with the agreement and list specific exceptions to the company’s promises, such as pending lawsuits, existing liens on intellectual property, or unusual contracts. They carve out known problems from the broad assurances the company makes in the main document, so read the schedules with the same care as the agreement itself.
Most startups do not draft from scratch. The National Venture Capital Association publishes a model stock purchase agreement that has become widely adopted in venture financings.1National Venture Capital Association. Model Legal Documents Online platforms like Clerky offer templates tailored to early-stage deals. A recognized template lowers legal costs and gives both sides a familiar starting point, though every deal still needs customization.
Promises Each Side Is Making
Representations and warranties are the factual statements each party makes about itself and the transaction. The company typically represents that it is properly incorporated, has the authority to issue the shares, owns its intellectual property free of undisclosed claims, and has no hidden liabilities beyond what appears in the disclosure schedules. If any of these statements turns out to be false, the company may owe the purchaser compensation under the indemnification provisions.
The purchaser makes promises too, and the most important one involves investment intent. The purchaser represents that they are buying the stock as an investment, not to immediately resell it. This representation ties to the private placement exemption under Section 4(a)(2) of the Securities Act of 1933, which allows companies to sell securities without registering them with the SEC as long as the offering is not made to the general public.2Office of the Law Revision Counsel. 15 USC 77d – Exempted Transactions The SEC has further clarified that general advertising and broad solicitation of investors are incompatible with this exemption.3U.S. Securities and Exchange Commission. Private Placements – Rule 506(b)
These promises are not permanent. The agreement specifies a survival period during which they remain enforceable, typically six to 24 months after closing. Fundamental representations like proper incorporation and authority to sell shares often survive longer than general business representations. Once the survival period expires, a party can no longer bring a claim for breach of that particular warranty.
Covenants are the forward-looking half. The company might promise to maintain business insurance, deliver periodic financial statements, comply with tax laws, or notify investors before taking certain major actions. Some covenants expire at closing; others run for the life of the investment. Indemnification is the enforcement mechanism behind representations and covenants alike, defining how the injured party gets compensated when something turns out to be false or broken. These clauses typically cap the total recovery and set a minimum threshold of losses before a claim can be triggered.
Rights That Come With the Shares
Buying common stock gives you a voice in how the company is run. Common shareholders generally receive one vote per share on major decisions like electing the board of directors or approving a merger.4Investor.gov. Shareholder Voting Many venture-backed companies create dual-class structures or grant preferred stockholders special voting rights that dilute common shareholders’ influence, so the agreement should spell out exactly what governance rights come with the shares you are buying.
Transfer restrictions control what you can do with your shares after closing. A right of first refusal is standard: before you can sell your shares to an outsider, you have to offer them to the company, and sometimes to other existing investors, first, at the same price and on the same terms. Some agreements add co-sale rights, which let other investors sell a proportional number of their shares alongside yours if you find a buyer.
Drag-along rights work in the opposite direction. If shareholders holding a specified majority approve a sale of the company, drag-along provisions force minority holders to participate on the same terms. Without them, a single small shareholder could block an acquisition everyone else wants. The triggering threshold is negotiable, and founders should pay close attention to whether it takes a simple majority or a supermajority to activate.
Preemptive rights protect existing shareholders from dilution when the company issues new shares in future rounds. If the agreement includes them, you get the chance to buy enough new shares to maintain your ownership percentage before those shares are offered to outsiders. These rights are not automatic under corporate law in most states; they exist only if the agreement or the corporate charter grants them.
Vesting and the Company’s Repurchase Right
Stock sold to founders and early employees almost always comes with a vesting schedule. You earn full ownership of your shares gradually over time rather than all at once. The standard arrangement is four years with a one-year cliff: nothing vests during the first twelve months, 25% vests at the one-year mark, and the remaining 75% vests in equal monthly installments over the next three years. If you leave the company before fully vesting, the company has the right to repurchase your unvested shares, usually at the original purchase price.
That repurchase right is the teeth behind the schedule. The agreement should state whether repurchase happens automatically when you depart or whether the company has to affirmatively exercise the option within a set window, often 90 or 120 days. Poorly drafted agreements that require action can create problems if the company misses the deadline, potentially leaving an ex-employee holding shares the company expected to get back.
When You Can Actually Sell
Vesting is not the only limit on liquidity. Shares acquired in a private placement are restricted securities. Under SEC Rule 144, you cannot resell them on the open market until you have held them for at least six months if the company files public reports, or one year if it does not.5Securities and Exchange Commission. Rule 144 – Selling Restricted and Control Securities Stock certificates for restricted shares carry a legend stating they cannot be transferred without registration or an applicable exemption, so the restriction is visible on the certificate itself.
Who Is Allowed to Buy
Most common stock sales in private companies rely on Regulation D exemptions, which impose rules about who can invest. An accredited investor is someone who meets at least one of the SEC’s financial thresholds: individual income above $200,000 (or $300,000 jointly with a spouse) in each of the two most recent years with a reasonable expectation of the same in the current year, or a net worth exceeding $1 million, excluding the value of a primary residence.6eCFR. 17 CFR 230.501
How rigorously the company must confirm accredited status depends on which Regulation D exemption it uses. Under Rule 506(b), the company needs only a reasonable belief that investors are accredited, based on the relationship and information it already has. Under Rule 506(c), which allows general solicitation and advertising, the company must take affirmative steps to verify accredited status. A simple checkbox where the investor self-certifies is not enough under either standard.7U.S. Securities and Exchange Commission. Assessing Accredited Investors under Regulation D
For Rule 506(c) offerings, the SEC provides specific verification methods: reviewing tax returns or W-2s for the income test, reviewing bank and brokerage statements for the net worth test, or obtaining written confirmation from a registered broker-dealer, attorney, or CPA who has independently verified the investor’s status. A prior verification remains valid for five years as long as the company receives a written representation and has no reason to doubt it.7U.S. Securities and Exchange Commission. Assessing Accredited Investors under Regulation D
The 83(b) Election and Its 30-Day Deadline
This is where most founders either save or lose a significant amount of money, and the window is brutally short. When you purchase restricted stock subject to a vesting schedule, the IRS treats each vesting event as a taxable moment. Without an election, you owe income tax on the difference between what you paid for the shares and their fair market value at the time they vest. For a startup that takes off over a four-year vesting period, that difference can be enormous.
A Section 83(b) election lets you short-circuit this by choosing to pay tax on the full value of the shares at the time of purchase, before any vesting occurs.8Office of the Law Revision Counsel. 26 USC 83 – Property Transferred in Connection With Performance of Services If you bought founder shares at $0.001 per share, the tax hit at that point is negligible. As the shares vest and the company’s valuation climbs, you owe nothing additional on the vesting. When you eventually sell, the gain is treated as a capital gain rather than ordinary income, which is typically taxed at a lower rate.
The catch: you must file the election with the IRS by mail within 30 days of receiving the shares. There is no extension and no electronic filing option. You also have to send a copy to the company.9Internal Revenue Service. Section 83(b) Election – Form 15620 Missing this deadline is irrevocable. The IRS will not grant relief, and you are stuck paying tax at vesting on whatever the shares are worth at that point. For a company whose shares go from $0.001 to $5.00 over a vesting period, the difference in tax liability can reach into the hundreds of thousands of dollars.
The election does carry a risk. If you leave the company and forfeit unvested shares, you do not get a refund on the taxes you already paid on those forfeited shares. For most early-stage founders paying tax on a tiny initial value, that risk is minimal compared to the potential savings.
Signing and Closing
Once the agreement is finalized, the parties sign it. Electronic signature platforms are standard, and the resulting documents carry timestamps and tamper-evident records. After signatures are in place, the investor wires the purchase price to the company’s designated bank account.
In community property states, the closing package often includes a spousal consent form. Nine states use a community property system, and in those jurisdictions, a married investor’s spouse may have a legal interest in the purchased shares. Companies require spousal consent to prevent a situation where a spouse later claims partial ownership and disrupts the capitalization table. Skipping this step is a common oversight in early-stage deals that surfaces during later funding rounds when new investors conduct due diligence.
Both sides should preserve all closing documents in an organized binder or secure digital folder. Future investors, acquirers, and auditors will expect to see a clean record of every equity transaction the company has completed.
What the Company Must Do After Closing
Update the Cap Table and Stock Ledger
Immediately after closing, the company updates its capitalization table to reflect the new shares. The cap table is the master record of who owns what: every shareholder, their share count, the class of stock, the price paid, and any vesting or restriction terms. Investors in future rounds will scrutinize it closely, and errors compound quickly as a company issues more equity over time. The stock ledger, a related but distinct record, tracks the sequential history of share issuances and transfers, including certificate numbers and shareholder addresses.
File Form D With the SEC
If the stock sale relies on a Regulation D exemption, the company must file Form D with the SEC no later than 15 calendar days after the first sale of securities in the offering.10eCFR. 17 CFR 239.500 – Form D, Notice of Sales of Securities Under Regulation D and Section 4(a)(5) of the Securities Act of 1933 The filing is made electronically through the SEC’s EDGAR system and reports the offering size, the exemption claimed, and information about the issuer and any brokers involved.11Securities and Exchange Commission. Frequently Asked Questions and Answers on Form D Missing this deadline does not automatically void the exemption, but it is a securities law violation that can draw regulatory scrutiny and complicate future offerings.
Handle State Blue Sky Filings
Federal Form D is only half the filing obligation. Most states also require a notice filing when securities are sold to their residents under a Regulation D exemption. Requirements, deadlines, and fees vary by state. Some require the filing before any sale to a state resident; others allow 15 days after the first sale. Failing to file can trigger late fees, cease-and-desist orders, and in some states investor rescission rights, meaning the investors can demand their money back plus interest. Companies selling to investors in multiple states should budget for these filings as part of closing costs.
Issue Certificates With the Restrictive Legend
The company issues a physical or electronic stock certificate to the purchaser. Shares acquired through a private placement carry a restrictive legend on the certificate stating that the securities have not been registered under the Securities Act and cannot be resold without registration or an applicable exemption. The legend stays on the certificate until the holder satisfies the conditions of Rule 144 or registers the shares, which in practice means holding them for at least six months (reporting companies) or one year (non-reporting companies) before any resale is possible.5Securities and Exchange Commission. Rule 144 – Selling Restricted and Control Securities