How Do SAFEs Work?

Most first cheques into a startup are not shares. They're a promise of shares: a SAFE, a convertible note, or a regional cousin like an ASA or a CCD. Founders sign these early and discover what they agreed to a year later, at the priced round, when everything converts at once.

So, how do SAFEs work? An investor wires cash today, and the document defines the price they'll eventually pay for shares, usually the better (for them) of a valuation cap or a discount on the next round's price. The rest of this lesson makes that sentence precise.

Why deferred pricing exists

To sell shares, you need a price. To have a price, you need a valuation, and valuing two people and a prototype is mostly guesswork. A priced round also means creating a new share class: preferred terms, charter amendments, weeks of legal drafting. For a first cheque of a few hundred thousand, that overhead is disproportionate.

Convertible instruments defer the pricing question to the next priced round, when a lead investor with more information sets a real valuation. The early cash converts into shares at that round, but not at the round's full price, which would mean paying the same as investors who waited. So the instrument carries terms rewarding the early risk: a valuation cap, a discount, or both.

Convertible notes did this job for decades as actual debt. In late 2013, Y Combinator published the SAFE (Simple Agreement for Future Equity), keeping the conversion mechanics but stripping out the debt: no interest, no maturity, no repayment obligation. It's now the default early-stage instrument in the US and beyond.

Post-money vs pre-money SAFEs: the 2018 shift

The original 2013 SAFE was what we now call pre-money: the cap was measured against the capitalization excluding the other SAFEs converting alongside it. So nobody could say what percentage a pre-money SAFE would buy until the round happened. Every additional SAFE changed the answer for everyone. Founders stacked SAFEs, added up the dilution wrong, and got a nasty surprise at conversion.

In 2018 YC replaced it with the post-money SAFE. The fix is elegant: the cap is defined to include all converting SAFEs (though not the new round money), collapsing the ownership calculation into one division:

Ownership = investment ÷ post-money valuation cap.

A 250k SAFE on a 5M post-money cap is 5%, locked in the day you sign, whatever you raise on other SAFEs afterwards. The certainty is real, but note who pays for it: each additional post-money SAFE dilutes only the founders and existing shareholders, never the other SAFE holders. Under the old pre-money form, everyone shared that dilution.

The useful habit follows directly: keep a running total of committed ownership (investment ÷ cap, summed across every SAFE) and treat it as already spent. The SAFE-stacking walkthrough runs a full multi-SAFE scenario.

Caps, discounts, and MFN

The valuation cap is a ceiling on the conversion price. If your next round values the company above the cap, the SAFE holder converts as if the company were worth the cap, buying in cheaper than the new money. A post-money cap fixes minimum ownership (investment ÷ cap); the higher your eventual round, the bigger the holder's price advantage.

The discount converts the SAFE at the next round's price minus a fixed percentage; 20% is the norm. On a round priced at 1.00 per share, the holder pays 0.80.

When a SAFE has both, the investor doesn't get both. It converts at whichever term produces the lower price per share, i.e. more ownership. The cap wins whenever the round prices meaningfully above it; the discount only matters in modest rounds close to the cap.

MFN, "most favored nation", is the third variant: an uncapped, no-discount SAFE with a clause letting the holder adopt the terms of any later, better convertible (a lower cap, a bigger discount). It lets the very first money come in before anyone is ready to argue about a number, without punishing it for moving first.

How conversion actually computes

A SAFE converts at your next equity financing, the priced round. Compute each applicable path, take the one that favors the investor, and issue that many preferred shares. For a post-money SAFE with both terms:

• Cap path: ownership = investment ÷ post-money cap. Fixed at signing.
• Discount path: ownership = investment ÷ ((1 − discount) × the round's post-money valuation).
• The SAFE converts on whichever path gives more ownership. The discount beats the cap only when the round's post-money is below cap ÷ (1 − discount).

Two refinements. First, SAFEs convert into a sub-series (Safe Preferred, or shadow preferred) with the same rights as the round's preferred except the price-based ones: the per-share liquidation preference matches what the holder actually paid, not the round price. Second, a round isn't the only trigger: in an acquisition before conversion, the standard post-money SAFE pays the greater of the money back or the value of converting at the cap; in a dissolution, the money comes back before anything flows to common.

One honest caveat: a single SAFE is easy, but a real round converts a stack of SAFEs while the option pool is topped up, a simultaneous system rather than a sequence of divisions. That's where spreadsheets quietly go wrong, and it's the problem Vquity's close-round wizard is built for: it converts the whole stack with a tested YC-style post-money engine, tops up the pool, and snapshots the pre-close cap table in one atomic step.

Convertible notes vs SAFEs

A convertible note does the same conversion job but is legally debt, which brings two extra moving parts:

• Interest. Notes accrue interest, typically 2–8% simple, usually not paid in cash but added to the principal and converted into shares alongside it. The longer a note sits, the more it converts.
• Maturity. Notes have a due date, commonly 18–24 months out. If no qualifying round has happened by then, the note is technically repayable, which most startups can't do. In practice the parties extend or negotiate a conversion; in the bad case, the investor holds a claim against an insolvent company. A SAFE has no maturity: it sits until a round, exit, or dissolution.

Notes often carry a qualified financing threshold: auto-conversion only if the next round raises a stated minimum. SAFEs convert at any bona fide equity round. Caps and discounts work the same way on both.

Why still use a note? Some investors want the downside protection of a debt claim; some jurisdictions handle debt more cleanly; and bridges between rounds often use notes precisely because maturity creates a forcing function. But the early-stage trend, especially in the US, is decisively toward SAFEs: fewer terms, no interest clock, no maturity cliff.

ASAs, CLNs, and CCDs: the regional cousins

Outside the US, the same deferred-pricing idea wears local clothing.

UK, the ASA. The Advanced Subscription Agreement is the UK's SAFE-alike, shaped by the SEIS/EIS tax-relief schemes behind much UK angel investing. To stay relief-compatible, an ASA must genuinely be equity-in-waiting: non-refundable, no interest, and it must convert by a longstop date, commonly six months, at the cap or a default price even if no round has happened. The longstop makes an ASA far more time-pressured than a SAFE.

UK, the CLN. The Convertible Loan Note is the UK's convertible note: real debt with interest and maturity, more paperwork than an ASA, and not SEIS/EIS-eligible. It's the standard choice for bridges and for investors who want a creditor's claim.

India, the CCD. The Compulsorily Convertible Debenture is a debenture that must convert into equity. Repayment at maturity isn't an option, and the conversion price or formula is fixed up front. The compulsion is regulatory: under India's foreign-investment rules, only instruments that must convert count as equity for FDI purposes; optionally-convertible ones are treated as external debt with stricter rules. CCDs (and their sibling, CCPS) are the workhorse convertibles for foreign money into Indian startups.

Singapore and much of Southeast Asia use SAFEs and CLNs close to the US and UK forms. The instruments rhyme everywhere; the defaults, deadlines, and tax hooks don't. See the regional equity differences lesson.

That's the instrument layer. Next: the priced round itself, with term sheets, pre- and post-money valuations, and how the price per share that everything above converts at actually gets set.