If you are raising pre-seed or seed capital, your first financing document will almost certainly be either a convertible note or a Simple Agreement for Future Equity (SAFE). Both instruments defer the valuation question to a later priced round, allowing founders to raise capital quickly without the expense and complexity of a full equity financing. But they are not interchangeable, and the choice between them has consequences that persist through every subsequent financing event.
How Convertible Notes Work
A convertible note is debt. The investor loans money to the company, and the loan converts into equity at a future priced round. Because it is debt, a convertible note has a maturity date — typically eighteen to twenty-four months — at which point the principal and accrued interest must either convert or be repaid.
The conversion mechanics are governed by two key terms. The valuation cap sets the maximum valuation at which the note will convert. If the company raises a priced round at a $20 million valuation but the note has a $10 million cap, the note holder converts at the $10 million valuation — effectively receiving shares at half the price of the new investors. The discount rate — typically 15 to 25 percent — provides an alternative conversion mechanism. If the priced round valuation is below the cap, the note holder converts at the round price minus the discount percentage.
Interest accrues on the principal, usually at a rate between 4 and 8 percent annually. This interest converts into equity alongside the principal at the conversion event, meaning the investor receives slightly more shares than the principal amount alone would purchase. Over a two-year period, this interest can increase the investor's resulting equity position by 10 to 16 percent above what a non-interest-bearing instrument would produce.
The maturity date creates a structural tension. If the company has not raised a priced round by maturity, the investor technically has the right to demand repayment. In practice, most note holders do not demand repayment from a company that cannot afford it — but the legal right creates leverage. Some notes include automatic conversion at maturity, converting the principal and interest into equity at the cap valuation. Others extend automatically. The maturity provision should be negotiated carefully because it defines the power dynamic if the company's fundraising timeline does not proceed as planned.
How SAFEs Work
The SAFE was introduced by Y Combinator in 2013 specifically to address the structural complications of convertible notes. A SAFE is not debt. It has no maturity date, no interest rate, and no repayment obligation. It is simply an agreement that the investor will receive equity at a future priced round, subject to a valuation cap and/or discount.
The simplicity is deliberate. A standard SAFE is a five-page document with minimal negotiation points. The investor wires money, the company issues the SAFE, and conversion happens automatically when the company raises a qualifying priced round. If the company never raises a priced round, the SAFE simply remains outstanding — there is no maturity event that creates a repayment obligation or conversion deadline.
In 2018, Y Combinator introduced the post-money SAFE, which changed how ownership dilution is calculated. Under the original pre-money SAFE, the founder and SAFE holder's ownership percentages depended on how much additional capital was raised at the priced round — making it difficult to know exactly how much of the company the SAFE represented. The post-money SAFE fixes the investor's ownership percentage at the time of investment, regardless of subsequent SAFE issuances.
This distinction matters enormously. Under a post-money SAFE with a $10 million cap, a $1 million investment represents exactly 10 percent of the company on a post-money basis. If the company issues additional SAFEs before the priced round, those additional SAFEs dilute the founders — not the prior SAFE holders. This is a meaningful shift in dilution mechanics that founders must understand before accepting post-money SAFE terms.
The Practical Differences
Founder Dilution
Post-money SAFEs create more predictable dilution for investors but can produce surprising dilution for founders who raise multiple SAFE rounds. Each additional SAFE is additive to the prior SAFEs, and all of that dilution comes from the founders' share. A founder who raises $500,000 on a $5 million post-money SAFE (10 percent) and then raises another $500,000 on the same terms (another 10 percent) has sold 20 percent of the company before the option pool expansion that will occur at the priced round.
Pre-money convertible notes share dilution across all stakeholders at the priced round, which generally produces less founder dilution when multiple instruments are outstanding. However, the dilution calculation is more complex and less predictable until the priced round terms are set.
Investor Protections
Convertible notes provide investors with more structural protections. The maturity date creates a contractual deadline. Interest accrual provides additional economic value. And the debt characterization gives the investor priority in a liquidation scenario — note holders are creditors who must be paid before equity holders receive anything.
SAFEs provide none of these protections. A SAFE holder has no recourse if the company never raises a priced round. There is no maturity date to trigger repayment, no interest to accrue, and in a dissolution scenario, SAFE holders are typically paid after creditors but before common shareholders.
This difference in investor protection affects who will accept each instrument. Institutional seed funds and experienced angels are generally comfortable with SAFEs because they understand the instrument and invest across a portfolio where individual outcomes are less critical. Friends-and-family investors and less experienced angels may prefer the structural protections of a convertible note, and the debt characterization may provide them with a better tax position if the investment fails.
Legal Cost and Complexity
SAFEs are significantly cheaper and faster to execute. A standard Y Combinator SAFE requires minimal legal review if the founder uses the template without modification. Convertible notes typically require more negotiation and customization, and the legal costs can range from $2,500 to $10,000 depending on the complexity of the terms and the number of investors.
For a founder raising $200,000 from five angel investors, the difference between executing five standard SAFEs and negotiating a convertible note with five investors can be measured in weeks and thousands of dollars. This efficiency advantage is one of the primary reasons SAFEs have become the dominant early-stage financing instrument in the venture ecosystem.
Which One to Use
The answer depends on three factors: your investor base, your fundraising timeline, and the norms in your market.
If you are raising from institutional seed funds or experienced angels in a major venture market (San Francisco, New York, Boston, Seattle), post-money SAFEs are the default instrument. Most investors in these markets prefer the simplicity and have standardized their processes around the Y Combinator template. Introducing a convertible note adds friction without meaningful benefit.
If you are raising from friends, family, or angels who are less familiar with venture mechanics, a convertible note may be more appropriate. The debt characterization is easier for non-venture investors to understand, the maturity date provides a defined timeline, and the interest accrual provides modest additional economic value that demonstrates respect for the investor's capital.
If you are raising in a market outside the traditional venture hubs — including many markets in Colorado, Virginia, and the Pacific Northwest — investor preferences may vary. The key is to understand what your specific investors expect and to avoid surprising them with an instrument they do not understand or have not evaluated.
Regardless of instrument, every founder should understand the conversion mechanics, the dilution implications, and the downstream effects on their cap table before signing. A thirty-minute conversation with experienced counsel about the specific terms of your financing instrument is one of the highest-return investments a founder can make.
This article provides general information about legal matters and does not constitute legal advice. Laws vary by state and individual circumstances. Please consult with a lawyer at Relevant Law to discuss your specific situation.