Flat, Up, or Down: The Real Valuation Mechanics of a Bridge

Why most founders get this wrong

Two failures dominate. The first is the founder who insists on a flat or up bridge when the evidence base will not defend it, walks the round to a halt, and ends up running a down bridge under more time pressure than necessary. The second is the founder who accepts a down bridge without modelling the anti-dilution-clause consequences, and discovers six weeks after close that the founder cap-table position has compressed by 8-15 percentage points more than expected.

Both failures share a root cause: the founder treated the price as the variable and the cap table as the constant. In a bridge, the cap table is the variable and the price triggers it. The anti-dilution clauses inside the existing instruments — broad-based weighted average, narrow-based weighted average, or full ratchet — determine how dilutive a given price actually is. Two bridges at the same nominal price can produce wildly different founder-dilution outcomes depending on what is buried in the original term sheet.

Warning: If the existing cap table contains full-ratchet anti-dilution protection (rare in UK Seed, more common in cross-border syndicates), a down bridge of even 15-20% can re-rate the founder position more than a 40% down round with broad-based weighted-average protection. Read the original term sheet before pricing the bridge.

What each direction actually signals

Flat. Reads as "the company has progressed to the level the last round priced; the bridge funds the next milestone". The next round prices on the bridge progress, not on the bridge price. This is the cleanest signal.

Up. Reads as "substantive evidenced progress that the last round did not anticipate". Credible only with documented milestones — material customer wins, IP grants, regulatory clearances. Without those, an up bridge reads as founder-led pricing that the next round will discount on its own diligence.

Down. Reads as "the last round mis-priced or the business has materially under-performed". The next round prices the bridge as a re-baseline; it does not pretend the down round did not happen. The strategic case for accepting a down bridge is when the alternative — an extension at flat that does not solve the problem — produces a worse next-round outcome.

Why "flat" is structurally underrated

Founders frequently treat a flat bridge as a disappointing outcome. In most situations it is the strongest one available. A flat bridge keeps the cap-table convention intact, avoids triggering anti-dilution clauses, leaves the next round's pricing anchor undisturbed, and signals to the wider market that the company is progressing along the trajectory the last round priced for. The pressure to negotiate "up" is almost always a founder-led pressure, not a partner-led one — partners generally prefer a clean flat bridge to a contested up bridge that sets up a difficult next-round conversation.

The exception is when the founder has documented evidence of milestones the last round did not anticipate — a major customer win, a regulatory clearance, an IP grant that materially expands the addressable market. In those cases an up bridge is defensible and the next round will accept the new anchor. Without the documented milestone, the up bridge becomes founder-led pricing that the next round discounts.

The strategic case for accepting a down bridge

Three situations make a down bridge the structurally right answer despite its costs. First, when the alternative is an extension at flat that does not solve the underlying capital-structure problem — a flat extension that runs out of money in nine months produces worse outcomes than a down bridge that runs out in eighteen. Second, when the existing investors have signalled that flat is not negotiable and the founder needs the capital to reach the next round on any terms. Third, when the down bridge is funded by a new lead with the conviction to set the priced re-baseline that the company actually needs to reach Series B from a clean cap table.

In each case, the down bridge is the best of the structurally available options, not the preferred one. The discipline is to negotiate the depth of the down step against the anti-dilution mechanism — every percentage point matters — and to use the new capital to produce the operational result that justifies the re-baseline. Down bridges that are followed by the milestones the bridge thesis promised tend to recover; down bridges that are followed by continued under-performance compound the cap-table compression at the next round.

How to apply it to your round

The decision sequence runs in order. Modelling the founder-dilution outcomes before negotiating is the discipline that distinguishes founders who walk into a bridge with their cap-table position intact from those who walk out with it compressed by more than they expected.

If the evidence supports a flat bridge. Anchor the conversation on flat. Existing investors who want to negotiate down should be answered with the asset-register evidence, not with founder protest. Partners price evidence; the asset register is the evidence.

If the evidence supports an up bridge. Verify the milestone documentation independently before pricing up. An up bridge that the next round considers founder-led pricing rather than evidence-led pricing damages the next round's anchor more than a flat bridge would have done.

If a down bridge is structurally the right answer. Negotiate the depth of the down step against the anti-dilution mechanism. A 15% step under broad-based weighted average is often less dilutive than a 5% step under full ratchet. Get the term-sheet read done first, then negotiate the price into the most cap-table-efficient zone.