What Is a Convertible Note? A Plain-English Guide for Founders
Early-stage startups have an awkward problem. They need money to prove their idea works, but it’s nearly impossible to put a fair price on a company that might only have a prototype, a few customers, and a pitch deck. Founders don’t want to sell equity at a rock-bottom valuation, and investors don’t want to overpay for something unproven.
The convertible note was designed to sidestep that standoff. It lets a startup raise money now and figure out the price later. Here’s how convertible notes work, what the key terms mean, a simple example of how they convert, and how they compare to the SAFE.
As always, I’m not a lawyer or financial advisor, and this is a plain-English explainer rather than advice. Fundraising documents have real legal and tax consequences, so bring in a professional before you sign one.
What Is a Convertible Note?
A convertible note is a short-term loan from an investor to a startup that is designed to turn into equity later instead of being paid back in cash. It usually converts when the company raises its next “priced” round, meaning a round where investors and the company agree on a specific valuation and share price, such as a seed or Series A round.
In other words, it starts life as debt and is expected to end life as stock. The investor lends money today, and in exchange, they get the right to convert that loan, plus interest, into shares at a better price than the investors who come in later.
Why Startups Use Convertible Notes
Convertible notes became popular in early-stage fundraising for a few practical reasons:
- They delay the valuation question. The company and investor don’t have to agree on what the business is worth today.
- They’re faster and cheaper than a priced round. A priced equity round involves more documents, more negotiation, and higher legal fees.
- They’re flexible. A startup can raise from different investors at different times without organizing a single formal round.
- They reward early risk. Features like discounts and valuation caps give early investors a better deal than later investors, which compensates them for betting early.
The Key Terms of a Convertible Note
Most convertible notes are built around the same handful of terms. Understanding these is most of the battle.
Principal
The principal is simply the amount the investor puts in. If an angel investor writes a $50,000 check, the principal is $50,000.
Interest Rate
Because a convertible note is technically debt, it accrues interest. Unlike a normal loan, though, the interest usually isn’t paid in cash. Instead, it gets added to the amount that converts into shares, so the investor ends up with slightly more equity.
Maturity Date
The maturity date is the deadline by which the note is supposed to convert or be repaid, often a year or two after it’s issued. If the company hasn’t raised a priced round by then, the note’s terms determine what happens next. The investor might be able to demand repayment, convert at a preset valuation, or agree to extend the deadline. In practice, extensions are common, because demanding repayment from a cash-strapped startup rarely helps anyone.
Valuation Cap
The valuation cap sets a maximum company valuation at which the note will convert. If the startup’s next round is priced at a higher valuation than the cap, the note holder converts as if the company were only worth the cap amount. This protects early investors from having their stake shrink if the company’s value soars before the next round.
Discount
The discount gives note holders a percentage off the share price paid by new investors in the next round. A 20% discount, for example, means the note holder pays 80% of the price new investors pay.
Many notes include both a cap and a discount. When that happens, the investor typically gets whichever one produces the lower price per share, not both.
Qualified Financing
Notes usually define what counts as the triggering event for automatic conversion, often called a “qualified financing.” This is typically a priced equity round above a certain dollar amount, which prevents a tiny raise from triggering conversion.
Change of Control
Notes also address what happens if the company is acquired before the note converts. Common options include letting the investor get their money back, sometimes with a multiple, or convert into shares right before the sale.
How a Convertible Note Converts: A Simple Example
The math is where convertible notes click for most people, so here’s a simplified example. Real conversions involve more detail, but the logic is the same.
Say an investor puts $100,000 into a startup through a convertible note with:
- A $5 million valuation cap
- A 20% discount
- A 5% annual interest rate
One year later, the startup raises a Series A at a $10 million pre-money valuation, and new investors pay $1.00 per share.
Now we figure out the note holder’s conversion price:
- Discount price: 20% off $1.00 is $0.80 per share.
- Cap price: The cap ($5 million) is half the round’s valuation ($10 million), so the cap price is half of $1.00, or $0.50 per share.
The investor gets the better of the two, which is $0.50.
After a year of 5% interest, the note is worth $105,000. Divide that by $0.50, and the investor receives 210,000 shares. A new Series A investor putting in the same amount at $1.00 per share would get roughly half that. That difference is the reward for investing early.
Convertible Notes vs SAFEs
If you’ve spent any time around startups, you’ve probably heard about the SAFE, or Simple Agreement for Future Equity. Y Combinator introduced the SAFE in 2013 as a simpler alternative to convertible notes, and its SAFE User Guide explains that the SAFE was intended to replace convertible notes for early-stage fundraising.
The two instruments work similarly. Both convert into equity in a future priced round, and both commonly use valuation caps and discounts. The biggest differences:
| Convertible Note | SAFE | |
|---|---|---|
| Legal form | Debt | Not debt; a contract for future equity |
| Interest | Yes, usually converts into shares | No |
| Maturity date | Yes | No |
| Repayment risk | Possible at maturity | No repayment obligation |
| Complexity | More terms to negotiate | Fewer terms, more standardized |
SAFEs have become very common in early-stage startup fundraising, especially in tech hubs. Convertible notes are still widely used, though, particularly by investors who prefer the protections that come with debt, like a maturity date and a creditor’s position if things go wrong. I’ll cover SAFEs in more depth in a dedicated post.
Pros and Cons of Convertible Notes
For Founders
Pros: faster fundraising, lower legal costs, no need to set a valuation too early, and flexibility to raise from investors over time.
Cons: the maturity date creates pressure, the interest adds dilution, and a low valuation cap can give away more of the company than founders expect. Stacking several notes with different caps can also make it hard to see how much ownership you’ve actually sold until the priced round arrives.
For Investors
Pros: a better price than later investors, interest that adds to their stake, and the protections of holding debt rather than a simple promise of future equity.
Cons: no ownership or voting rights until conversion, uncertainty about what they’ll ultimately own, and the risk that the company never raises a priced round or fails before converting.
A Few Things to Keep in Mind
Convertible notes are securities. Even though they’re simpler than a priced round, issuing them is still selling securities, which means federal and state securities laws apply. Many early-stage raises rely on exemptions that limit sales to accredited investors. The SEC’s small business resources explain the role of accredited investors in private fundraising, and it’s worth understanding before you start taking checks.
The fine print matters. The note itself, and often a separate note purchase agreement, will include representations about the company, conditions, and other legal terms beyond the headline economics. Just like any business contract, those sections deserve a careful read. If you want a sense of how much weight a single paragraph can carry, my post on the indemnification clause shows how a clause most people skim can decide who pays when something goes wrong.
Model the dilution. Before issuing notes, run the numbers on how they’ll convert under different scenarios. A cap table tool or a spreadsheet can save you from an unpleasant surprise when your Series A closes.
The Bottom Line
A convertible note is a loan that’s meant to become equity. It lets startups raise money quickly without agreeing on a valuation, while giving early investors a discount, a valuation cap, or both as a reward for taking the risk. It’s simpler than a priced round, but it still carries real obligations, including interest, a maturity date, and securities law requirements.
For founders, the key is understanding exactly how your notes will convert and how much of the company they’ll represent when they do. For investors, it’s understanding what protections you have if the company never gets to that next round. Either way, the numbers in the note matter far more than the simplicity of the paperwork suggests.
