Short answer: a convertible note is debt that accrues interest and has a maturity date. A SAFE is not debt, has no interest and no maturity date, and converts into preferred stock when the company raises a priced round. Both are used to take early money without setting a share price. The SAFE is shorter and has fewer terms to negotiate; the note gives the investor a creditor’s position and a deadline.
“SAFE note” is a common search phrase, but a SAFE is not a note. That distinction drives most of the differences below.
This is general information, not legal or tax advice.
Clause by clause
| Clause | Post-money SAFE (YC form) | Convertible note (terms vary by document) |
|---|---|---|
| Legal nature | Right to future equity | Loan |
| Interest | None | Accrues at a stated rate; converts with principal if the note says so |
| Maturity date | None | Yes; repayment or a negotiated outcome at maturity |
| Valuation cap | Post-money cap (cap version) | Can include a cap, frequently stated pre-money |
| Discount | Discount-only version available | Can be combined with a cap |
| Conversion trigger | Any priced preferred round; no minimum size | A “qualified financing” above a size set in the note |
| On a sale of the company | Greater of money back or as-converted amount | Repayment, a multiple of principal, or conversion, per the note |
| On a shutdown | Purchase amount, junior to creditors | Repayment as a creditor, ahead of stockholders |
| Pro rata rights | Optional side letter | Negotiated separately if at all |
The SAFE column comes from Y Combinator’s SAFE page and its SAFE user guide. YC offers three US versions: valuation cap with no discount, discount with no cap, and an uncapped MFN. Notes have no single published form, so that column describes terms notes can contain rather than one document.
Debt or not
A noteholder is a creditor. If the company shuts down, the note gets repaid before stockholders. The YC SAFE places the investor’s cash-out right junior to outstanding debt, including convertible notes that are not converted, and on par with other SAFEs and preferred stock.
Interest and maturity
These two terms are where notes create work.
Assumptions
- $500,000 invested
- Note: 6% simple annual interest, 24-month maturity
- Priced round closes 18 months after funding
Note: interest = $500,000 x 6% x 1.5 years = $45,000
amount converting = $545,000
SAFE: amount converting = $500,000 (no interest)
If no priced round happens before maturity, the note is due. The company then negotiates an extension, a conversion, or repayment it may not be able to afford. A SAFE has no such date.
Conversion mechanics
The post-money SAFE’s cap includes all SAFE money but not the priced round’s new money or its pool increase. YC’s guide puts the result simply: ownership sold equals investment divided by the post-money cap. A $500,000 SAFE at a $10,000,000 post-money cap converts to 5% before priced-round dilution. Notes with pre-money caps dilute each other, so ownership depends on how much else was raised on notes. The cap table template works a two-SAFE conversion through to a Series A.
Cost and speed
The YC SAFE is one standardized document, and its own text says the parties have not modified the form beyond filling in blanks. A note invites more negotiation: rate, maturity, qualified financing size, sale treatment. Each term is a reason to involve lawyers.
When a note still fits
Some investors simply prefer a debt instrument. A note’s maturity date gives the investor a pressure point if the company drifts without raising a priced round, and some investors want that. A company that expects a priced round within months, from a lead who has already been identified, may also accept a short note as a bridge.
For a first raise, simplicity is the main argument for the SAFE, and it fits the formation sequence in how to start a startup company. Whatever the instrument, the sale is a securities offering: Rule 506(b) limits and the Form D filing within 15 days of the first sale apply either way, per the SEC’s 506(b) page.
Also consider
- A priced seed round, when an investor wants board seats, protective provisions or information rights from the start.
- YC’s uncapped MFN SAFE, for an early check where neither side wants to set a cap yet.
- A SAFE with YC’s pro rata side letter, for an investor whose main ask is the right to follow on.