MFN clauses explained: how later terms flow backward

A most-favoured-nation (MFN) clause is a promise to an early investor: if you ever give anyone better terms, I automatically get them too. It sounds like a small courtesy. In a SAFE stack it quietly does two things — it raises that investor's ownership and it removes your freedom to price the next SAFE cheaply. Here's exactly how much it costs, with numbers.

What the clause actually does

An MFN holder inherits the best (lowest cap, highest discount) terms of any qualifying instrument you issue before conversion. So an early SAFE that looks generous to you on paper can silently reprice to a much tighter cap the moment you sign a cheaper SAFE later. The dilution shows up at conversion, not when you sign — which is why it's so easy to under-count.

Worked example

Two SAFEs and a modest option pool:

• Founders: 9,200,000 shares.
• Lead SAFE: $500,000 at a $6,000,000 cap. No MFN.
• Syndicate SAFE: $300,000 at an $8,000,000 cap — with an MFN clause.
• Priced round: $3,500,000 of new money at an $18,000,000 pre-money, targeting a 10% post-round option pool.

Without the MFN, the syndicate SAFE would convert on its own $8M cap. But the MFN reaches across the stack, sees the lead's cheaper $6M cap, and adopts it. Both SAFEs now convert at the same $6M-cap price:

Compare that to what the syndicate SAFE would have taken on its own $8M cap. A higher cap means a higher price, which means fewer shares — roughly three-quarters of the shares (8M/6M inverse). The MFN adds shares to the syndicate at the founders' expense.

The second, sneakier cost: lost pricing flexibility

The dilution above is the visible cost. The invisible one is strategic: once an MFN holder is in your stack, every subsequent SAFE you sign is also, in effect, a discount to them. Want to give a new angel a tight $5M cap to close them fast? The MFN holder inherits that $5M cap too. The clause quietly converts your cap table into a ratchet — the best terms you ever grant become the terms your MFN holders hold.

What to do about it

• Inventory every MFN before you raise the next dollar. You need to know which holders will inherit whatever you sign next.
• Model the stack as it will actually convert, not as each document reads in isolation. An MFN SAFE's stated cap is not its conversion cap.
• Price later SAFEs knowing the backflow. A cheap late SAFE is more expensive than it looks if MFN holders share in it.