Every successful funding round carries a pleasant paradox: the company is worth more, but the early investor slice of the pie gets smaller. Dilution is the mathematical consequence of issuing new shares, and for a foreign investor entering at Series A the question is never whether dilution happens, but how much, in which scenario, and which clause in the investment documents will push back when a later round prices lower. Distinguishing percentage dilution from value dilution is the first step to negotiating correctly.
The Legal Framework You Need
Vietnamese law gives shareholders no default anti-dilution right beyond the pre-emptive right to buy newly issued shares. Under Article 125 of the Law on Enterprises 59/2020/QH14, in a private placement existing shareholders may buy in proportion to their holdings within the charter deadline; an investor who pays follows the round and keeps its percentage, one who does not accepts dilution. Any stronger anti-dilution mechanism, such as adjusting a conversion price or issuing bonus shares at nominal value after a down round, is a creature of contract: it must be written into the shareholders agreement and subscription documents and, to bind the company and future shareholders, reflected in the company charter.
For a foreign investor, each new round is also a separate investment law event: a new investor entering, or an existing one increasing its stake, must be checked against sector market-access conditions, the foreign ownership ceiling and the capital contribution registration cases under the Law on Investment 143/2025/QH15. A practical point often forgotten is that when anti-dilution triggers, it changes the foreign investor ownership percentage, and that change must also stay inside the permitted ceiling. An anti-dilution clause drafted without regard to the ownership cap can become unenforceable exactly when the investor needs it most.
Applying the Rules to a Real Deal
Dilution works on two levels. The first is mechanical percentage dilution: an investor holding 20 percent after Series A sees that stake fall to roughly 16 percent if Series B issues new shares equal to a quarter of the existing capital to a new investor, with nobody doing anything wrong. The second is value dilution, which occurs only in a down round priced below the previous round: the early investor loses percentage and per-share value simultaneously. Pre-emptive rights handle level one if the investor has follow-on money; anti-dilution clauses exist to handle level two, by resetting the effective purchase price of the early investor.
The two common anti-dilution formulas differ sharply in harshness. Full ratchet resets the early investor entire purchase price to the lowest later price, maximising investor protection but punishing founders heavily and potentially frightening later rounds away. Weighted average, in broad-based and narrow-based variants, blends the old and new prices by the volume of capital involved, producing a gentler adjustment and remaining the balanced market choice. When negotiating later-round protection, investors should lock three layers together: pro-rata pre-emptive rights plus super pro-rata over others unsubscribed portions, early information rights on the new round, and the chosen anti-dilution formula with a defined expiry.
Illustrative example: A Singapore venture capital firm entered Series A of a Vietnamese healthtech startup with broad-based weighted average anti-dilution and a contractual information covenant. The Series B eighteen months later priced 25 percent lower after a market correction. The formula adjusted the firm conversion price and issued a measured top-up, while founders, who had modelled the clause at signing, accepted the outcome without a dispute. The new lead investor later cited the predictable, pre-agreed adjustment mechanics as a reason the round could close quickly despite being a down round.
Procedure and Documents to Prepare
First: model ownership across rounds under up, flat and down round valuation scenarios. Next: choose the anti-dilution formula: broad-based or narrow-based weighted average, or full ratchet, with an expiry. After that: write anti-dilution, pre-emptive and super pro-rata rights into the shareholders agreement and reflect them in the charter. Then: check the foreign ownership ceiling so top-up shares on a trigger stay within permitted limits. Finally: at each new round, exercise information and pre-emptive rights on time and reconcile any anti-dilution trigger with the issuance file.
- model ownership across rounds under up, flat and down round valuation scenarios.
- choose the anti-dilution formula: broad-based or narrow-based weighted average, or full ratchet, with an expiry.
- write anti-dilution, pre-emptive and super pro-rata rights into the shareholders agreement and reflect them in the charter.
- check the foreign ownership ceiling so top-up shares on a trigger stay within permitted limits.
- at each new round, exercise information and pre-emptive rights on time and reconcile any anti-dilution trigger with the issuance file.
Common Risks and How to Prevent Them
The first risk is holding pre-emptive rights only, with no anti-dilution, so a down round erodes both stake and value. The second risk is choosing an overly harsh full ratchet that demotivates founders and deters later investors. The third risk is an anti-dilution trigger that would push foreign ownership above the sector ceiling, making the clause unusable. The safeguard is modelling all three valuation scenarios before choosing a formula and drafting the clause with counsel checking the ownership ceiling at each trigger point.
An anti-dilution clause is only usable if triggering it does not push the investor through the foreign ownership cap; an elegant formula that becomes unlawful the moment it operates is worth nothing. Model all three valuation scenarios before choosing the formula, and verify the ownership cap at every trigger point.
Frequently Asked Questions
How is my stake diluted through Series A and B rounds?
Dilution across rounds follows simple arithmetic: each time the company issues new shares to incoming investors, the total share count rises while your share count stays fixed, so your percentage falls. Holding 20 percent after Series A, a Series B issuing shares equal to a quarter of the existing capital leaves you near 16 percent. The important point is that a lower percentage does not automatically mean lower value: if Series B doubles the company valuation, the new 16 percent can be worth more than the old 20 percent. Only in a down round, priced below the previous round, do you suffer both layers of dilution at once.
How do anti-dilution rights work?
Anti-dilution works by resetting the early investor effective purchase price when the company issues shares more cheaply later. With weighted average, the adjusted price blends old and new prices weighted by the capital volumes involved, and the investor receives top-up shares compensating part of the loss. With full ratchet, all of the early investor shares are repriced at the lowest later price, the strongest protection but heavily reverse-dilutive to founders. The mechanism is purely contractual and must be written into the shareholders agreement and the charter to be enforceable in Vietnam.
What should be watched when negotiating protective terms in later rounds?
Four points matter when negotiating later-round protection. First, lock pro-rata pre-emptive rights plus the right to buy portions other shareholders decline, so you can actively defend your percentage when you believe in the company. Second, limit the duration and scope of the anti-dilution clause rather than leaving it hanging over every future round forever. Third, demand early information rights on new round terms, because anti-dilution can only be calculated correctly if you know the exact issue price and volume. Fourth, as a foreign investor, re-check the sector ownership ceiling at trigger time so top-up shares stay within legal limits.
