TL;DR
An MFN clause, or most favoured nation clause, is language that can let an Investor elect or receive later better terms offered to another Investor in a similar financing. It is often used when an early instrument is otherwise uncapped, lightly negotiated, or meant to keep terms flexible.
What an MFN clause can affect
Y Combinator includes an uncapped MFN post-money SAFE form among its published US company documents. The practical founder lesson is broader: when MFN language exists, later financing terms need to be reviewed against earlier signed instruments. Source: Y Combinator SAFE documents.
| Later term | Why MFN holders care | Founder response |
|---|---|---|
| Lower valuation cap | May give better conversion economics. | Check whether earlier Investors can elect that cap. |
| Higher discount | May reduce conversion price. | Model dilution if the discount spreads. |
| Side letter rights | May create information or pro rata expectations. | Track all side letters in one summary. |
| Conversion trigger | May change when or how shares are issued. | Review trigger language with counsel. |
Also Read: Valuation cap vs discount
MFN checklist for founders
- Create a table of every SAFE, note, and side letter with MFN language.
- Before offering new terms, check whether earlier Investors can adopt them.
- Model dilution if the better term applies to every MFN holder.
- Keep notices, consents, and amendments in the Data Room.
- Do not describe a later term as "one-off" until MFN language is reviewed.
Bottom line
MFN language is not automatically bad. It can help close an early check when final terms are uncertain. The problem is operational: founders lose control when they cannot trace which Investors can inherit which later terms.