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Convertible Notes

Convertible Notes: The Complete Guide for Startup Founders and Investors

By Joe Wallin,

Published on Apr 9, 2026   —   20 min read

Startup FinancingFundraisingStartup LawValuation CapSAFEs
Business meeting representing startup fundraising

Summary

Convertible notes are debt instruments that convert to equity at your next priced round. Here's everything founders need to know about terms, mechanics, tax implications, and common mistakes.

Convertible Notes: The Complete Guide for Startup Founders and Investors

When founders first come into my office to discuss raising capital, convertible notes inevitably come up. And for good reason. They've become the de facto instrument for seed-stage financing over the past two decades, replacing more formal preferred stock rounds and creating a faster, cheaper path to capital for early-stage companies. But here's what I see happen repeatedly: founders and investors use convertible notes without fully understanding how they work, what can go wrong, and how to negotiate terms that actually protect their interests.

In This Guide

I've been practicing startup law in Washington state for a long time now, and I've closed hundreds of convertible note rounds. I've also seen the disasters that happen when founders don't understand the mechanics of conversion, when notes stack up without clear conversion triggers, and when the accounting gets messy. This guide is built from that real-world experience. I'm going to walk you through exactly how convertible notes work, why certain terms matter enormously, and how to negotiate a deal that serves your business rather than creating future complications.

What Is a Convertible Note, Really?

At its core, a convertible note is a hybrid instrument. It starts life as debt—a promissory note that obligates your company to repay a specific principal amount plus interest. But it has a special feature: under certain conditions, that debt converts into equity. This is the key feature that makes convertible notes fundamentally different from traditional bank loans, and it's why they've become so popular in startup financing.

Think of it this way. An investor gives you money today as a loan. Your company owes them that money, plus interest, on the maturity date. But if certain events happen before maturity—typically a qualified financing round where you raise a larger amount of money at a pre-negotiated valuation—the note automatically converts into shares of preferred stock at favorable terms.

This creates an elegant solution to a genuine early-stage problem. Founders and early investors have wildly different views on valuation. A founder thinks their company, with an incredible team and a huge market opportunity but minimal traction, is worth $5 million. An investor thinks it's worth $1 million, or maybe they haven't even thought about valuation yet. A convertible note lets both parties kick that valuation question down the road until the company has more data and the fundraising environment becomes clearer.

Why not just issue preferred stock immediately? Because that requires a 409A valuation, board meetings, stock option plan discussions, and all the administrative overhead of a formal equity round. Convertible notes are faster and cheaper to document, which is why they became the instrument of choice for pre-seed and seed rounds.

The Key Terms You Need to Understand

Principal is straightforward: it's the amount of money the investor is putting in. If you take a $100,000 convertible note investment, the principal is $100,000. This is the base amount that will eventually either be paid back or converted into equity.

Interest rate is the annual rate at which the debt accrues interest. Seed-stage convertible notes typically carry interest rates between 3% and 8% annually, though this has varied based on broader interest rate environments. The interest accrues over time and is usually added to the principal amount at conversion. So if you take a $100,000 note at 5% interest for two years, you'll convert approximately $110,250 into shares instead of just $100,000. Founders often overlook this, but it materially affects how much dilution they take when they finally raise an equity round.

Maturity date is when the convertible note officially comes due. This is typically 18 to 24 months after issuance, though some notes have longer terms. If the note hasn't converted into equity by the maturity date, and no qualified financing has occurred, the note becomes problematic. The company technically owes the principal plus accrued interest back to the investor in cash. Most early-stage companies can't pay this, which leads to tense negotiations and sometimes forced conversions or amendments.

Valuation cap is one of the two most important terms in a convertible note, and I want to give it careful attention. The valuation cap puts a ceiling on the valuation used for conversion. Here's why this matters. Imagine you take a $500,000 convertible note with a $10 million valuation cap. Eighteen months later, your company has grown dramatically, and you're raising a Series A at a $50 million post-money valuation. Without a cap, the note would convert at that full $50 million valuation. But with the cap, the note converts as if the company was valued at $10 million, giving the earlier investor a discount on the shares they receive. This reward for early risk-taking is central to how convertible notes work.

Discount is the other crucial conversion mechanism. Some notes use a discount instead of (or in addition to) a valuation cap. A discount is a percentage reduction applied at conversion. A note with a 20% discount converts at 80% of whatever valuation is used in the qualified financing round. So if you raise a Series A at a $30 million valuation, a note with a 20% discount converts at $24 million.

The interaction between caps and discounts is one of those details that trips up founders. If a note has both a cap and a discount, typically whichever is more favorable to the investor is applied. We'll get into this more deeply in a moment.

How Conversion Actually Works at a Qualified Financing

Let me walk through a concrete example so you understand the mechanics precisely.

Your company takes a $500,000 convertible note from an angel investor at a 5% interest rate, with a $15 million valuation cap and a 20% discount. The investor plans to hold the note for up to two years. Twelve months later, your company has traction, and you're raising a Series A. You've closed commitments for $5 million at a $40 million post-money valuation (which means a $35 million pre-money valuation).

When this Series A closes, the convertible note automatically converts. Here's how:

First, calculate the principal plus accrued interest. You have $500,000 principal. At 5% annual interest, after one year you've accrued $25,000, bringing your total to $525,000.

Second, determine which conversion mechanism applies. The note has a $15 million cap and a 20% discount on the Series A price. The Series A uses a $35 million pre-money valuation. Apply the discount: $35 million times 80% equals $28 million. So the cap ($15 million) is more favorable to the investor than the discounted valuation ($28 million). The note converts using the $15 million cap.

Third, divide the note amount by the Series A price per share to calculate how many shares the noteholder receives. Let's say the Series A pricing is set at $2.00 per share (calculated by dividing the $35 million pre-money valuation by shares outstanding). The noteholder's $525,000 converts at the capped valuation of $15 million, meaning they effectively buy shares at $525,000 / ($15,000,000 / $2.00) = $525,000 / 7,500,000 shares = $0.07 per share (roughly). They receive 7,500,000 shares, while the Series A investors pay $2.00 per share.

This is the magic of convertible notes for early investors. They get a significant discount to later investors, rewarding their risk-taking.

Valuation Caps Versus Discounts: When Each Matters

I've had founders ask me why a note would ever include both a cap and a discount. The answer is that early investors want to protect themselves in different scenarios.

The valuation cap is the real insurance policy. If your company explodes in value—you're raising Series A at $100 million valuation—the cap ensures the early investor isn't completely left behind. They still get the reward of a significant discount relative to new Series A investors.

The discount, meanwhile, is protection against a more modest scenario. If you raise a Series A at a valuation below the cap, the discount ensures the early investor still gets some benefit for going in early. Maybe you raise at a $12 million pre-money valuation—below your $15 million cap. The 20% discount brings it down to $9.6 million effectively, still better than a straight equity deal at $12 million.

In practice, when a note has both cap and discount, the calculation is: which conversion method is more favorable to the investor? That's the one that applies. This is typically spelled out as "the greater of the valuation cap or the discounted valuation."

So what's the right combination? Honestly, it depends on the dynamics and risk profile. Early-stage notes often have caps in the $5-15 million range and discounts of 15-30%. Later-stage convertible notes (less common, but they exist) might have higher caps and lower discounts. The further along you are, the easier valuation conversations become, so there's less need for dramatic discount mechanisms.

The Awkward Conversation: What Happens at Maturity?

Here's the scenario no one wants to discuss, but it happens more often than people admit: the maturity date approaches, and your company hasn't raised a qualified financing. Maybe you've decided to bootstrap. Maybe the fundraising environment got tough. Maybe you're in that weird position where you have product traction but haven't found a Series A yet.

Technically, the note is due. The company owes the principal plus accrued interest in cash. If you can't pay it, you have a serious problem. You've essentially defaulted on a loan.

In practice, founders and investors usually sit down and find a solution. Sometimes the note gets extended—the maturity date is pushed out another year. Sometimes it converts to equity anyway, even without a qualified financing, using a mutually-agreed valuation. Sometimes the note gets amended on different terms. But these conversations are never fun, and they would be much easier to avoid with clearer documentation and more realistic planning upfront.

This is why the maturity date matters enormously. A company that might raise a Series A in 20 months should not take a note with an 18-month maturity. You're creating an artificial deadline that could force bad decisions. Similarly, if you've taken multiple notes, staggered maturities can create a cascade of problems. If five notes mature within a month of each other and you haven't raised a qualified financing, you're managing five separate negotiations simultaneously.

My practical advice: think carefully about your fundraising timeline when you agree to maturity dates. And if you take multiple notes, try to align maturities so you're not managing dozens of separate conversations with investors.

Convertible Notes Versus SAFEs: A Practical Comparison

One question founders constantly ask me is whether they should use a convertible note or a SAFE (Simple Agreement for Future Equity). SAFEs were created by Y Combinator in 2013 explicitly to be even simpler than convertible notes, and they've become increasingly popular.

The key difference: a SAFE is not debt. It's not a promissory note at all. It's a contract that says "if certain conditions are met, the investor will get equity." But until those conditions are met, there's no debt obligation. The investor isn't a creditor. The company doesn't have any obligation to repay the investor in cash.

This simplifies a lot of things. There's no interest accrual. There's no maturity date (though SAFEs can have pro-rata investment rights that trigger in future rounds). There's no debt on the balance sheet, which can be important for some financial calculations and for loans from banks or other creditors.

So when should you use notes versus SAFEs? I'll be direct: for most early-stage companies raising their first $500,000 to $1 million, SAFEs are probably fine. They're faster, cheaper, and the investor protections are honestly comparable for that stage. The noteholder isn't going to collect on a debt anyway if your startup fails.

I recommend convertible notes when: (1) you're raising a meaningful amount of money where the interest accrual actually matters financially, (2) you're dealing with sophisticated investors who expect debt documentation, (3) you anticipate a longer time to Series A and want clearer terms on what happens if that doesn't occur, or (4) you want the protection of a formalized debt instrument that gives you more contractual specificity. I've written extensively about SAFEs elsewhere on this blog, and that post goes into detail on the specific terms.

For this guide, I'm focusing on convertible notes because they're still the standard instrument and they require more careful analysis of complex terms.

Debt Characteristics: Promissory Note, Security Interest, and Subordination

When you take a convertible note, you're signing a promissory note. That's an unconditional written promise to pay the principal plus interest to the investor. This is important legally, because it makes the investor a creditor of your company, not an equity holder.

Most convertible notes include a security interest, meaning the investor has a lien on company assets. This is standard in seed-stage investing. The security interest is recorded on the UCC (Uniform Commercial Code) filing to give the investor priority over other creditors. In practical terms, if your company goes under and is liquidated, the convertible note investor gets paid before holders of junior unsecured debt, though after senior secured creditors like banks.

Subordination is the flip side of this. When you later raise a Series A, the Series A investors will typically require that the convertible notes be subordinated to their debt (if any) and explicitly provide that the notes convert and are not paid off in a Series A financing. Otherwise, the Series A investors would be lending money to a company with senior creditors who had to be paid first in any liquidation.

This gets important in Section 409A tax planning and in how the balance sheet looks. Convertible notes are sometimes classified as debt for balance sheet purposes and sometimes as a hybrid. The accounting depends on the specific terms and how close the note is to conversion. I've worked with controllers and CFOs who had strong opinions on this point, and honestly, it's nuanced. But it's worth discussing with your accountant.

Interest Accrual: The Hidden Dilution Multiplier

I've noticed that founders focus intensely on valuation caps and discounts but often gloss over interest accrual. This is a mistake.

When you take a $100,000 note at 5% annual interest for two years, you don't just owe $100,000 at conversion. You owe approximately $110,250. That's $10,250 in additional equity being issued to the investor, with no additional cash invested. Multiply this across multiple notes, and it compounds.

Here's a real-world example from my practice: Founder took three separate convertible notes over 18 months. Note 1: $200,000 at 5%. Note 2: $150,000 at 6%. Note 3: $100,000 at 5%. By the time they raised a Series A, the aggregate principal had grown from $450,000 to approximately $480,000 just from interest accrual. That's an extra $30,000 in equity being issued.

Some note agreements specify that interest is only added at conversion, while others accrue interest monthly. Some provide for simple interest (straight percentage each year), while others use compound interest (interest on the interest). These differences matter, though for most seed-stage notes the spread isn't enormous.

The practical implication: when you're projecting your fully diluted capitalization table and how much equity will be issued in your Series A, make sure you're accounting for accrued interest on all convertible notes. Ask your investors for the exact terms, and do the math.

Qualified Financing Thresholds: What Triggers Automatic Conversion?

Convertible notes don't automatically convert whenever you raise any amount of money. The note typically specifies what qualifies as a "qualified financing," and this is important.

A typical definition is something like: "any equity financing of at least $500,000 or more at a fixed valuation, resulting in the sale of shares designated as preferred stock." The threshold can vary—some notes set it at $250,000, others at $1 million. Some notes say "either a Series A or a Series B," understanding that you might skip Series A and go straight to Series B.

Why does this threshold matter? Because if you raise a small financing that's below the threshold, the convertible note doesn't convert automatically. It stays a note. This creates complexity because now you have a mix of equity and convertible debt on the cap table, and you're tracking multiple instruments.

There's also the question of what counts as a "qualified financing" beyond just size. Typically, acquihires or secondary transactions don't trigger conversion. A strategic investment from a customer or partner might not, depending on how the note defines it. And this creates room for disputes.

My recommendation to founders: push for a lower qualified financing threshold ($250,000 rather than $1 million) to increase the likelihood that your first "real" equity round will trigger conversion. A lower threshold also incentivizes investors to actually close the Series A rather than string out a series of smaller pre-Series A rounds. And be very explicit in the definition of "qualified financing" so there's no ambiguity later.

Most Favored Nation Clauses: The Secret Feature You Need to Understand

A lot of convertible notes include a "most favored nation" clause, and I've found that most founders don't actually understand how these work.

The MFN clause says something like: "If the company issues another convertible note with more favorable terms to any other investor, the terms of this note automatically adjust to match." So if you take a $500,000 note with a $12 million cap, and then six months later you take another $500,000 note with a $10 million cap, the first investor's cap automatically steps down to $10 million.

This creates obvious incentives to issue all your convertible notes on consistent terms, because if you don't, your earlier investors will demand MFN adjustments automatically. Some notes even include MFN on pricing, so if you raise any note at a better valuation cap, all earlier notes adjust.

The reason this matters to founders is that it limits your flexibility in fundraising. If you're taking notes at different times from different investors, and market conditions change, you might want to take a later note on slightly different terms to reflect new information about your company. MFN clauses make that harder.

I typically recommend negotiating narrowly scoped MFN clauses that only apply to notes raised within a specific time window (say, within 90 days) or that only adjust on certain terms (cap, but not discount). This preserves your flexibility while giving earlier investors reasonable protection against being immediately undercut by a slightly later investor.

Amendment and Waiver Provisions: Why These Matter

Every convertible note agreement specifies how it can be amended. Can you amend it unilaterally? Must all investors agree? Can the company and a majority of investors amend over the objection of a dissenting investor?

This becomes critical if you need to extend a note's maturity date, adjust the conversion trigger, or modify other terms. If your note says "amendments require unanimous written consent," and you have eight investors with notes outstanding, you need all eight to agree to any change. That's a recipe for disputes and gridlock.

I usually recommend notes that allow amendments to key terms (maturity, qualified financing threshold) with consent of holders representing the majority of principal outstanding. This prevents any single investor from blocking a reasonable modification that most investors agree with, while still protecting minority investors from having terms changed unilaterally.

Similarly, waiver provisions let the company ask investors to waive certain rights—for instance, waive the requirement that a certain financing be "qualified" so the note converts anyway. These should be negotiable, and you want to understand upfront what flexibility you'll have if circumstances require it.

Securities Law Considerations: Regulation D and Accredited Investors

Here's where startup law gets technical, but it's important. Convertible notes are securities. They're not exempt from securities law just because they have a nice, streamlined document.

In practice, most convertible notes are issued under Regulation D (specifically, Rule 506), which exempts certain securities offerings from registration if you comply with specific conditions. The two main paths are Rule 506(b), which allows non-accredited investors but requires you to provide certain disclosures, and Rule 506(c), which allows only accredited investors but doesn't require disclosure.

Most seed-stage companies use Rule 506(b), which means you can take money from friends and family who aren't accredited investors, but you have to provide them with financial statements and other specific information. You can't just take their money and hand them a note with no other paperwork.

What's an accredited investor? Generally, someone with a net worth over $1 million or annual income over $200,000 ($300,000 if married). There are other categories too, like companies and certain institutional investors. But the point is: if you're taking notes only from accredited investors, you can use Rule 506(c) and don't need to provide detailed financials. If you're taking notes from friends and family, you probably need Rule 506(b), and you need to provide them documents.

I've seen founders overlook this entirely, taking convertible notes from investors without considering whether they're in compliance with Regulation D. The consequences can be serious. The offering could be deemed non-exempt, making the notes unregistered securities and giving investors rescission rights (meaning they can demand their money back).

My practical advice: before you issue convertible notes, confirm with your lawyer which Rule 506 exemption you're relying on, and make sure you follow the requirements. This usually means either (1) getting confirmations that all investors are accredited, or (2) providing investors with financial statements and specific disclosures. It's not hard, but it's important.

Tax Implications: OID, Interest Deductions, and Debt-Equity Characterization

Tax considerations are often overlooked, but they matter. There are three main issues to understand.

First, Original Issue Discount (OID). If you issue a convertible note with a discount (say, $100,000 principal with a 20% discount), there's an OID. The noteholder has paid less than the stated principal, and that difference is treated as interest for tax purposes. The accrual of OID over time is taxable income to the investor, even though they haven't actually received any cash. This is why sophisticated investors care about convertible note terms—OID affects their tax position.

Second, interest deduction. Your company gets to deduct interest paid on the note on its tax returns. But here's the catch: the IRS might recharacterize the note as equity if the terms are too equity-like. If the note has no fixed maturity date, or if repayment is contingent on your company's financial success, the IRS might say "this isn't really debt, it's equity," and disallow the interest deduction. This is rare with properly drafted convertible notes, but it's possible if terms are structured in unusual ways.

Third, debt versus equity characterization more broadly matters for balance sheet accounting, credit metrics, and securities law calculations. Generally, convertible notes are treated as debt until conversion, at which point they become equity. But again, the specific terms matter, and an accountant should review the note.

I typically recommend that founders have a tax advisor review any convertible note structure, particularly if the notes have unusual terms or if you're taking significant amounts of capital this way. It's not expensive to get this right, and it prevents complications later.

Common Mistakes: How Founders Get This Wrong

After years of practicing startup law, I've seen patterns in what goes wrong with convertible notes. Let me share the most common mistakes so you can avoid them.

Stacking notes without managing the dilution. Founders take three, four, sometimes five convertible notes without fully understanding how much equity they'll be diluted when these convert. A founder with no dilution takes a $100k note with a $5M cap, then another $100k with a $6M cap, then another $100k with a $5.5M cap. By the time you're raising a Series A, you might have $300k+ in principal plus interest converting, all at different terms, creating a complex cap table. Project your dilution upfront. Know exactly how much equity you're committing to.

Accepting maturity dates that don't align with your fundraising plan. If you believe you'll raise a Series A in 18 months but you take a note with a 18-month maturity, you're playing with fire. You're one month of delay away from having a note come due with no qualified financing to trigger conversion. Push for maturity dates that give you a 6-12 month runway beyond your projected Series A timing.

No valuation cap. I've occasionally seen founder-friendly investors take notes with no cap. This is extremely rare and probably a mistake on the investor's part. But if someone offers you a note with no cap, understand what you're getting: the investor is taking enormous risk for no downside protection. They're betting their entire return on your company's success. The flip side is their upside is unlimited. Make sure you understand the terms you're signing.

Unclear qualified financing thresholds. Taking notes with a "Series A" qualified financing trigger sounds clear until you haven't raised a Series A but you have raised a Series A-like round from a single investor or a group. Get specific. Define the dollar threshold, the instrument type, and the investor profile. "Any equity financing of $500,000 or more resulting in the sale of shares of Series Seed preferred stock or later series" is clearer than "a Series A."

Forgetting about interest accrual in cap table projections. I've worked with founders who projected they'd have 15% founder dilution at Series A, only to discover it was 18% because they didn't account for interest on three convertible notes. Interest accrual is real. Account for it.

Mixing notes with different MFN provisions.** If some notes have MFN and others don't, you create asymmetries. One investor demands MFN adjustments when they see you took a better deal elsewhere, while other investors don't have that right. Standardize your note terms. If you're taking multiple notes, they should all have consistent caps, discounts, interest rates, and MFN provisions.

Practical Advice for Negotiating Convertible Note Terms

So how do you actually negotiate a convertible note? Let me give you practical advice from the founder side.

Start with a form term sheet. There are standard forms available online—the Fenwick & West form, the Wilson Sonsini form, the SAFE documents. Use something that exists rather than negotiating from scratch. Negotiation is much easier when you're modifying known terms rather than writing custom language.

Valuation cap is the key variable. If I'm advising a founder, I prioritize getting a reasonable valuation cap. The cap is where the investor gets their upside protection, and it's what determines how much dilution you take in your Series A. Push on this first. I'd rather have a slightly higher interest rate or longer maturity if it means a lower cap.

Align maturity dates. If you're taking multiple notes, push hard to have the same maturity date for all of them. If that's not possible, stagger them so no more than two mature within a 30-day window. This prevents a cascade of debt maturity problems.

Keep the qualified financing threshold realistic. If you genuinely believe your Series A will be $2-3 million, don't agree to a $5 million qualified financing threshold. You'll end up with a note that doesn't convert automatically and causes problems. Be conservative and realistic in your projections.

Negotiate MFN narrowly. If you must accept an MFN clause, limit its scope. "MFN applies only to convertible notes issued within 90 days of this note" is better than "MFN applies to any convertible note issued within 18 months." Similarly, "MFN applies to valuation cap only" is better than "MFN applies to all terms."

Clarify amendment procedures. Push for a provision that allows amendments to certain terms (maturity, qualified financing threshold) with consent of noteholders representing 60% of principal. This prevents a single obstinate investor from blocking a reasonable modification.

Get securities law right.** Before you issue notes, confirm with a lawyer whether you're complying with Regulation D and what investor disclosures are required. This is cheap insurance and prevents huge problems.

Use a lawyer. I know this might seem self-serving coming from a startup lawyer, but it's true. Convertible notes might seem straightforward, but they have technical elements. A lawyer can spot issues with a form term sheet that would cost you meaningfully later. The legal cost of getting a note done right the first time is trivial compared to the cost of fixing it later if something goes wrong.

Building Your Series A from a Strong Note Foundation

Done right, convertible notes are actually a bridge that makes your Series A simpler. All those notes convert automatically into your Series A, adding a known amount of shares to your cap table. The Series A investors understand this and price accordingly. You have a clean path to completing your financing round.

Done wrong—with misaligned terms, unclear triggers, excessive stacking, or interest accrual you didn't account for—convertible notes become an obstacle. They complicate your Series A negotiations, create unexpected dilution, and sometimes derail the entire round because the cap table got too messy.

The key is to approach convertible notes thoughtfully. Understand the mechanics. Understand the compounding effect of multiple notes. Project the dilution. Negotiate terms that align with your actual funding timeline. And when in doubt, get legal advice before you sign.

If you're raising capital through convertible notes or any other structure, getting the legal foundation right is critical. I offer a free introductory call to discuss your startup's capitalization and financing strategy. Let's talk about how to structure your fundraising in a way that serves your business long-term. Schedule your free call here.

For more on startup fundraising and securities law, see our Complete Guide to Regulation D, Rule 506(b) vs. 506(c) Comparison, and Accredited Investor Rules.

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