A convertible debt agreement is a loan to a company, usually a startup, that can later turn into ownership shares instead of being repaid in cash. The investor puts money in now, the company records it as debt, and when a defined event happens later, the outstanding balance converts into equity at terms set in the contract. Founders use these agreements to raise capital between priced rounds because they postpone the hard question of what the company is actually worth, while still getting cash in the bank.
Before signing one, you need to understand five things: what the loan itself looks like, how the conversion math works, what triggers conversion, what protections sit inside the document, and what legal and tax rules apply on top of it.
The Loan Terms Underneath the Conversion
The principal is the cash the investor wires to the company. Until conversion, it’s a liability on the balance sheet, because legally it’s debt.
Interest usually runs 5% to 8% per year on startup notes. It doesn’t get paid out monthly. It accrues and gets added to the balance, so when conversion happens, the investor gets equity credit for both the original principal and the accumulated interest.
Every note carries a maturity date, typically 18 to 24 months after funding. If nothing has triggered conversion by then and the note hasn’t been repaid, the investor can demand cash. Most startups don’t have that cash sitting around, so in practice the parties negotiate an extension. The leverage that creates for the investor is the point.
Most convertible notes are unsecured. No specific company asset backs them. If the company defaults, the investor has a general claim, not a right to seize particular property. Many notes also include a subordination clause, which puts the noteholder behind senior lenders (like a bank line of credit) in the repayment queue. In a bankruptcy, senior creditors get paid first, subordinated noteholders next, and equity holders last. The instrument sits in the middle of the capital structure because it starts as debt and is expected to become equity.
How the Conversion Price Gets Calculated
Two terms control how many shares the investor receives at conversion: the valuation cap and the discount rate. Most agreements include both, with language saying conversion uses whichever produces the lower price per share for the investor.
Valuation Cap
The cap sets a ceiling on the valuation used to price the investor’s shares. If the cap is $5 million and the company later raises at a $10 million valuation, the note converts as if the company were worth $5 million. The noteholder ends up with roughly twice the shares of someone writing a fresh check at the priced round. The cap is how the earliest money gets rewarded for the earliest risk.
Discount Rate
The discount is a percentage reduction off the price new investors pay in the next round. Typical discounts run 15% to 25%. If new investors pay $1.00 per share and the note carries a 20% discount, the noteholder converts at $0.80.
The accrued principal plus interest is divided by whichever calculated price is lower, and that’s the share count.
What Triggers Conversion
Conversion isn’t at anyone’s whim. The agreement lists specific events that flip the debt into equity.
- Qualified financing. The most common trigger. The company closes a priced equity round of at least a stated size, and the note automatically converts into the same class of shares the new investors are buying. The threshold is negotiated upfront, often one to two times the total raised in the note round itself. Set it too high and the note lingers through smaller rounds; set it too low and conversion fires before the company is ready for it.
- Sale or merger. If the company is acquired before a qualified financing, the note usually gets repaid in cash: principal plus accrued interest. Some agreements add a repayment premium on top, compensating the investor for losing the equity upside.
- Maturity. If the note reaches its maturity date without a qualifying round or a sale, some agreements let the investor convert into common stock at a pre-negotiated price. That’s a fallback to avoid a cash repayment the company probably can’t make.
Investor Protections to Watch For
Most Favored Nation Clause
A most favored nation (MFN) clause lets an earlier investor adopt better terms the company gives to later noteholders. If you take an uncapped note and the company later issues capped notes, an MFN clause lets you pull in that cap. Without one, the earliest and riskiest money can end up with the weakest deal.
Anti-Dilution Protection
Anti-dilution provisions kick in if the company later issues shares at a lower price than earlier rounds (a down round). Two forms exist. A full-ratchet clause resets the investor’s conversion price all the way down to the new, lower price. A weighted-average clause blends the old and new prices and share counts to produce an adjusted conversion price somewhere in between. Weighted-average is far more common, because full-ratchet is punishing for founders.
Convertible Note or SAFE
A SAFE (Simple Agreement for Future Equity) is the other instrument you’ll see at early stages, and the two get confused constantly. The core difference matters: a convertible note is debt; a SAFE is not.
- Convertible notes accrue interest. SAFEs don’t. Over 18 months, that interest turns into extra equity at conversion.
- Convertible notes have a maturity date. SAFEs don’t. A SAFE holder can’t demand repayment if nothing ever triggers conversion.
- Convertible notes sit on the balance sheet as liabilities. SAFEs don’t fit neatly in any accounting category, which can complicate audits and later-round due diligence.
SAFEs are simpler and cheaper to close, which is why they dominate the earliest deals. Convertible notes give investors more structure and more leverage.
Securities Law Compliance
A convertible note is a security under federal law. Selling one triggers SEC registration requirements unless an exemption applies. Nearly all startup notes rely on Regulation D, specifically Rule 506(b) or Rule 506(c).
Rule 506(b) lets the company raise an unlimited amount from an unlimited number of accredited investors, plus up to 35 non-accredited investors, but bars general solicitation or public advertising. Adding non-accredited investors triggers extra disclosure obligations most startups avoid.
Rule 506(c) allows public advertising of the offering, but every investor must be accredited, and the company must take reasonable steps to verify that status rather than accept self-certification.
An accredited investor is generally someone earning over $200,000 individually (or $300,000 with a spouse) in each of the prior two years with a reasonable expectation of the same, or with a net worth over $1 million excluding a primary residence. Holders of Series 7, 65, or 82 licenses also qualify.
After the first sale, the company must file Form D with the SEC within 15 calendar days, through EDGAR. If the deadline lands on a weekend or holiday, it shifts to the next business day. Most states require their own notice filings under blue sky laws, with fees varying by state. Skipping state filings can bring penalties and may jeopardize the Regulation D exemption itself.
What You Need in Place to Sign
The document needs the full legal names and registered addresses of both parties, the exact principal, the interest rate, and the maturity date. The company should have a current capitalization table showing every existing shareholder and any outstanding convertible instrument. Without it, the conversion math can’t be modeled, and later investors will flag the gap in due diligence.
Before anyone signs, the board of directors should pass a formal resolution authorizing the note and the future issuance of shares on conversion. That resolution goes into the corporate minute book and blocks later arguments that the borrowing was unauthorized.
The agreement should specify governing law, usually the state where the company is incorporated. Once signed, the investor wires the principal and the company delivers a countersigned promissory note. That signed note is the investor’s proof of the debt and the conversion terms attached to it.
Amending or Extending the Note
Notes don’t always convert on schedule. If the maturity date arrives without a qualified financing, the parties have to extend the note or deal with a default. Most well-drafted agreements allow amendments with the consent of the company and holders of a majority of the outstanding principal, so a single small noteholder can’t block an extension the rest support.
Common amendments push back maturity, adjust the cap or discount to reflect changed market conditions, or add new conversion triggers. Every amendment should be signed and in writing. Handshake extensions create ambiguity that surfaces painfully during the next round of financing.
Tax Treatment
Convertible notes create tax exposure that can catch both sides off guard. On the company side, accrued interest is generally deductible as a business expense even though no cash moves during the accrual period. On the investor side, that same accrued interest may be taxable as ordinary income before any cash is received or the note converts, depending on how the instrument is structured.
The IRS applies original issue discount (OID) rules to debt instruments, convertible notes included. If a note is issued below face value, or if the conversion feature creates what the IRS treats as a contingent payment, the analysis gets more complex. Under IRC Section 1272, holders of debt with OID must generally include a portion of that discount in gross income each year on a constant-yield basis, whether or not any payment arrives.
Conversion itself is generally not a taxable event for either side if it follows the original terms of the agreement, and the investor’s basis in the new shares typically equals the principal and accrued interest that converted. But if the conversion terms get modified in a way the IRS treats as a deemed exchange of the old note for a new instrument, that modification can trigger tax. Run any amendment past a tax advisor before signing it.