Is a SAFE debt or stock?

A SAFE is not debt and not a loan—it has no interest and no maturity date. It isn’t stock until it converts into preferred shares when your startup raises an equity financing.

Does a SAFE convert in any equity financing?

Yes. When your company sells shares of preferred stock in an equity financing, the outstanding SAFEs convert automatically. There is no minimum raise required to trigger the conversion.

What happens if an investor wires less or more than the SAFE amount?

A small mismatch (usually a few dollars from wire fees or currency conversion) almost never causes a real problem. The investor owes any shortfall, so the cleanest fix is to ask them to wire the difference or cover it yourself. For an overpayment, keep the exact SAFE amount and refund the rest.

Does a SAFE ever expire?

A SAFE has no maturity date. It is designed to expire and terminate only when the investor has received stock in an equity financing or a liquidity event occurs. In theory, a SAFE could remain outstanding for a long time without needing to extend any dates.

Can a SAFE be amended?

Yes, with the written consent of the issuing company and the investor. Amendments across a series of SAFEs with the same terms can be made with a majority-in-interest of those investors, but an individual investor’s purchase amount can’t be changed without their consent.

How much ownership does a SAFE sell?

On a post-money valuation cap SAFE, ownership sold equals the investment divided by the valuation cap. For example, $500k on a $6.7M cap is about 7.5%. For discount or MFN SAFEs, the exact ownership sold is determined at the equity financing.

Founder guide

What a SAFE is and how it works for startups

A SAFE (Simple Agreement for Future Equity) is a contract an investor signs to fund your startup now in exchange for shares later. It converts automatically when your startup raises a priced round. The post-money SAFE is the Y Combinator standard since 2018.

Last checked 22 October 2026 against 3 official pages · 5 min read

2013
Year SAFE was created: 2018
Year post-money SAFE became standard: 10–20%
Common discount rates: 2 minutes
Time to send a SAFE

What is a SAFE

A SAFE is a short contract an investor signs to fund your startup now in exchange for the right to shares later. It is not debt—it has no interest and no maturity date. It converts into shares automatically when your startup raises a priced round (an 'equity financing').

The SAFE was created at Y Combinator in 2013. It is the most common way early-stage startups raise early investments. Thousands of startups have used it, raising billions over a decade.

Post-money SAFE explained

A post-money SAFE has a valuation cap that is 'post-money,' meaning it includes the SAFE investment. The post-money SAFE has been the YC standard since 2018.

The biggest advantage of the post-money SAFE is that the amount of ownership sold is immediately transparent and calculable. Ownership sold equals the investment amount divided by the valuation cap. For example, $500k on a $6.7M post-money cap is about 7.5%.

The post-money valuation cap is 'post' all the money you raise on SAFEs. It is not 'post' the equity financing money or the new or increased option pool adopted as part of the equity financing.

Valuation cap and how it works

The valuation cap is the highest valuation at which a SAFE converts into shares. If your startup’s priced round values the company above the cap, the SAFE converts at the cap instead. This rewards the investor for backing your company early.

Ownership sold equals the investment amount divided by the valuation cap. For example, $1M on a $6.7M cap sells about 15%. Raise less on that cap and you sell less: $500k is ~7.5%, $800k is ~12%.

If the equity financing prices your startup above the SAFE’s cap, the cap applies. If the round prices below the cap, the SAFE converts at the price per share paid by new investors.

Discounts on SAFEs

A discount rewards early investors with a lower price than your startup’s next priced round. On a 20% discount SAFE, the investor converts at a price per share that is 20% below the price per share in the equity financing. Discounts are commonly 10–20%.

Discount SAFEs convert at the discounted price per share paid by new money investors in your priced round. The exact ownership sold will be determined at the equity financing.

MFN (Most Favored Nation) SAFE

An MFN SAFE has no valuation cap or discount. Instead, it automatically takes the best terms of any SAFE you issue later. This lets an early investor fund your startup now without having to decide on a cap or discount.

The MFN SAFE adopts the best terms of any SAFE your startup issues later. The date used is the later of signing the SAFE or receiving the wire. Close your lower valuation cap SAFEs (fully wired) before issuing an uncapped MFN to control the terms.

When a SAFE converts

A SAFE converts automatically when your startup raises a priced round (an equity financing). There is no minimum raise required to trigger the conversion. The SAFE then terminates and the investor becomes a stockholder.

SAFE holders receive a 'shadow' series of preferred stock (e.g., Series A-2) alongside the new investors' standard preferred stock (e.g., Series A-1). The SAFE preferred stock carries the same rights, privileges, and seniority as the new investors' stock, except for the initial conversion price.

If your startup is acquired, goes public, or shuts down, the SAFE treats these as a 'Liquidity Event' or 'Dissolution Event.' In the valuation cap SAFE, the investor gets the greater of 1x their money back or what they’d receive if the SAFE had converted to common stock. In a shutdown, the investor gets their SAFE purchase amount back.

Pro rata rights and side letters

Pro rata rights let an investor invest money into your future priced round to maintain their percentage ownership. These rights are optional and live in a separate, standardized pro rata side letter, not in the SAFE itself.

If an investor wants pro rata rights, MFN, or information rights, keep the SAFE unmodified and use a side letter. Evaluate whether to grant these rights based on the amount the investor is investing. An investor buying a $500k SAFE has a better case for pro rata rights than one investing $10k.

Step by step

1
Send a SAFE using YC’s tool
Use 'Send a SAFE,' the official YC tool, to generate, sign, and send a SAFE in about two minutes. It is free and programmatic. To use it with an AI agent, install the YC CLI by running: curl -fsSL https://bookface.ycombinator.com/cli/install.sh | bash. Log in with yc login --device, verify the install with yc safes --help, and set up your company with yc safes setup. You can then list, create, update, and send SAFEs. Never run yc safes send without first confirming the exact terms.

Frequently asked questions

Is a SAFE debt or stock?: A SAFE is not debt and not a loan—it has no interest and no maturity date. It isn’t stock until it converts into preferred shares when your startup raises an equity financing.
Does a SAFE convert in any equity financing?: Yes. When your company sells shares of preferred stock in an equity financing, the outstanding SAFEs convert automatically. There is no minimum raise required to trigger the conversion.
What happens if an investor wires less or more than the SAFE amount?: A small mismatch (usually a few dollars from wire fees or currency conversion) almost never causes a real problem. The investor owes any shortfall, so the cleanest fix is to ask them to wire the difference or cover it yourself. For an overpayment, keep the exact SAFE amount and refund the rest.
Does a SAFE ever expire?: A SAFE has no maturity date. It is designed to expire and terminate only when the investor has received stock in an equity financing or a liquidity event occurs. In theory, a SAFE could remain outstanding for a long time without needing to extend any dates.
Can a SAFE be amended?: Yes, with the written consent of the issuing company and the investor. Amendments across a series of SAFEs with the same terms can be made with a majority-in-interest of those investors, but an individual investor’s purchase amount can’t be changed without their consent.
How much ownership does a SAFE sell?: On a post-money valuation cap SAFE, ownership sold equals the investment divided by the valuation cap. For example, $500k on a $6.7M cap is about 7.5%. For discount or MFN SAFEs, the exact ownership sold is determined at the equity financing.

Official sources

Rules and amounts change. Check these before you apply.

The SAFE — the open standard for startup fundraising | Y Combinator — ycombinator.com
SAFE conversion calculator | Y Combinator — ycombinator.com
SAFE vs. convertible note vs. priced round | Y Combinator — ycombinator.com

How this guide was made: StartupReader wrote it with AI from the official pages above, read on 22 October 2026. Every figure and name in it was checked automatically against those pages, and anything they don't support was left out. It's re-checked every month. It isn't affiliated with the program. Spotted something out of date? Tell us.