The business angel just wired €50,000 through a BSA Air. Three months later, you open your cap table while prepping your Seed: how many shares does the BA get at conversion, and what does it cost you in percentage points? The impact of a BSA Air isn't measured at signing, but at conversion, when your qualified round happens. The formula: Shares received = Investment / min(round price × (1 − discount) ; cap / total shares). Example: solo founder (1M shares), you raise €200K in BSA Air (cap €8M, discount 20%), then a Seed at a €10M pre-money. The BA gets 25,000 shares, or 2.44% post-conversion before the VC round. This guide gives you the full worked example, the trap of multi-round BSA Air, and the checklist to fold it all into your sheet. A lawyer is mandatory before signing for the legal nuance.
Quick recap: what is a BSA Air, in 30 seconds
A Bon de Souscription d'Actions Accord d'Investissement Rapide gives the investor the right to subscribe to shares under conditions set in advance, at a price calculated at the moment of conversion. The BA puts in cash now without locking a valuation. That valuation is set later, at your next qualified round (typically the Seed).
For the full mechanics, tax treatment, and background, see the full BSA Air guide. Here, we stay focused on the cap table impact.
How BSA Air dilution is calculated, plainly
The formula, in one line
Number of shares received = Investment / conversion price per share
The conversion price per share is whichever is most favorable to the Air investor. Two candidates:
- Price via the discount: price per share of the qualified round × (1 − discount)
- Price via the cap: valuation cap / total number of shares at the moment of conversion
The BA gets the lower of the two. That's the reward for coming in early.
When the cap bites, when the discount bites
If your Seed happens at a valuation above the cap, the cap applies: the BA pays for their shares pro rata to the cap. If your Seed happens below the cap, the discount applies. At the break-even point (Seed valuation = cap / (1 − discount)), the two prices converge.
Mini example: €200K, cap €8M, discount 20%, Seed at €10M
Solo founder, 1,000,000 shares. You raise €200,000 in BSA Air (cap €8M, discount 20%). Twelve months later, a Seed at a €10M pre-money.
- Price via the cap: 8,000,000 / 1,000,000 = €8/share
- Price via the discount: (10,000,000 / 1,000,000) × 0.80 = €8/share
- The two converge (a teaching case). Price applied: €8.
- BA shares: 200,000 / 8 = 25,000 shares
Post-conversion, the BA holds 25,000 / 1,025,000 = 2.44%, before the VC round. The VC who invests next dilutes you too, on that same basis.
Full worked example: from solo founder to seed round
An example rolled out in four steps, showing what happens at each move.
Step 0: initial cap table
You're coming out of an incubator, you haven't brought anyone on yet. Your cap table fits on one line.
| Shareholder | Shares | % |
|---|---|---|
| Founder | 1,000,000 | 100% |
| Total | 1,000,000 | 100% |
Step 1: a first BA puts €50K into a BSA Air
Cap €5M, discount 20%, deadline 18 months. The BA wires €50,000. They don't receive shares straight away: they receive a BSA Air, which will convert at the Seed.
On the cap table, nothing moves in issued shares. At the bottom of the table, you add a "BSA Air pending" line that records the commitment.
| Shareholder | Shares | % | BSA Air pending |
|---|---|---|---|
| Founder | 1,000,000 | 100% | n/a |
| BA 1 | n/a | n/a | €50,000 @ cap €5M, discount 20% |
On paper, you're still at 100%. In reality, you've already diluted part of your future cap table. Most founders underestimate this line.
Step 2: three more BAs in the same round
You close an additional €150,000 on the same terms. Total BSA Air outstanding: €200,000.
| Shareholder | Shares | % | BSA Air pending |
|---|---|---|---|
| Founder | 1,000,000 | 100% | n/a |
| BA pool (4 people) | n/a | n/a | €200,000 @ cap €5M, discount 20% |
Still 100% on paper. The dilution has multiplied by 4 in the future.
Step 3: Seed at a €8M pre-money, €1.5M ticket
Twelve months later, a VC comes in. Post-money €9.5M.
First, we convert the BSA Air:
- Price via the cap: 5,000,000 / 1,000,000 = €5/share
- Price via the discount: (8,000,000 / 1,000,000) × 0.80 = €6.40/share
- Min = €5/share. The cap bites.
- Shares received by the BA pool: 200,000 / 5 = 40,000 shares
Then, we calculate the VC price, fully diluted (the pre-money already includes the converted BSA Air):
- VC price: 8,000,000 / (1,000,000 + 40,000) = €7.69/share
- VC shares: 1,500,000 / 7.69 = 195,122 shares
Final cap table, line by line
| Shareholder | Shares | Final % |
|---|---|---|
| Founder | 1,000,000 | 80.96% |
| BA pool (converted BSA Air) | 40,000 | 3.24% |
| VC Seed | 195,122 | 15.80% |
| Total | 1,235,122 | 100% |
You went from 100% to 80.96%. The BSA Air cost you roughly 3.2 extra points of dilution compared to a scenario without one (84.2%). The reward: €200K twelve months earlier, without negotiating a valuation when it would have been lower.
The trap of multi-round BSA Air
Why 3-4 BSA Air on different terms wrecks your cap table
First BA in June at a €5M cap. Second in September at a €7M cap (you landed a client). Third in December at an €8M cap (you're starting to generate revenue). Three sets of terms, three conversion prices, three calculations to run in parallel at Seed time.
The VC who sees this has two possible reactions: either they agree to model the whole thing (rare if they're junior), or they ask you to harmonize, even to buy back the older BSA Air before they come in. Guess what that costs in lawyer hours.
The concrete case: BSA Air 1 at a €5M cap, BSA Air 2 at a €7M cap
Two BSA Air: €80K at a €5M cap, €120K at a €7M cap. At your Seed on a €10M pre-money, BSA Air 1 converts at the €5M cap (price €5), BSA Air 2 at the €7M cap (price €7). Two investors pay different prices for the same underlying share. Legally defensible, but your sheet has to record the two lines separately.
The simple recommendation: harmonize or group
If you bring several BAs in over several months, set a single subscription window (one BSA Air round with a deadline) on the same terms. That's what specialist lawyers recommend. You negotiate once, and the next VC doesn't wince.
Discount, cap and floor: a recap to understand the calculation
Discount (10-25% typical)
The reduction applied to the price per share of the next round. SeedLegals analyzed thousands of contracts: two thirds of BSA Air deals land between a 10% and 20% discount. The canonical site bsa-air.fr gives the official 15-25% range.
Valuation cap (€1M to €3M at seed, €5M to €8M for a bridge)
The valuation ceiling applied at conversion. SeedLegals finds €1M to €3M post-money at the French seed stage. For a bridge before Seed, expect €5-8M depending on your traction.
Floor (often set low)
The floor is mandatory under French law (Code de commerce). It protects you: if you raise in a crunch below it, the conversion happens at the floor, not lower. SeedLegals contracts show a cap equal to 2 × the floor in most deals.
For a clause-by-clause negotiation of these three parameters, see discount, cap, valuation: how to negotiate in 2026.
How to fold a BSA Air into your cap table sheet
Before conversion: a "BSA Air pending" line
Create a "BSA Air pending" tab. For each signed BSA Air, note: amount, cap, discount, floor, deadline, estimated conversion date. At the bottom, calculate an estimate of converted shares (optimistic and pessimistic scenarios). The VC looking at your cap table should see this line right away, not discover it during due diligence.
After conversion: issued shares and new %
At Seed signing, you convert. The BSA Air pending disappears, and a line of ordinary shares appears under each BA's name. You recalculate every % in the table (founder, ESOP, BSA Air, VC).
Recommended tools
Three options depending on your stage:
- Carta (carta.com): the US VC reference. Expensive, but what VCs ask for at Series A.
- SeedLegals cap table: built into their BSA Air platform, free if you sign with them.
- Google Sheet template: Eldorado publishes a free downloadable template, enough at pre-seed/seed.
4 BSA Air cap table mistakes to avoid
1. A cap too low relative to your plan
If you sign at a €3M cap and your Seed happens at a €10M pre-money, the BA converts at the cap and captures massive dilution. Align your cap with what you're aiming for in 12-18 months, not with what you get "easily" now.
2. Too many BSA Air on different terms
Covered above. Three BSA Air at three different caps means a VC who asks for harmonization first, or who values your company lower.
3. Ignoring "pending" BSA Air in the equity round negotiation
The pre-money you quote the VC must already include the converted BSA Air. Otherwise, you realize too late that the €8M pre-money you thought you were worth is actually €7.5M effective for you.
4. Confusing a BSA Air with a convertible bond
The BSA Air is an equity-linked security, not debt. A convertible bond (OC) is debt that converts. The OC can be repaid in cash if you don't raise, whereas the BSA Air converts automatically at the qualified round. Check what your lawyer puts in the contract.
And what about conversion in a failed raise or a liquidation?
If you don't raise before the deadline, or if the company enters insolvency proceedings, the BSA Air shifts to a different regime. We cover it in the dedicated guide: BSA Air in liquidation or dissolution.
FAQ
Does a BSA Air dilute immediately or only at conversion?
At conversion only. As long as the BSA Air isn't converted, no shares are issued and your equity % stays unchanged. In practice, any serious VC models the future dilution from due diligence onward: consider yourself already diluted on the economic paper, even if not yet on the legal paper.
What's the maximum BSA Air you should have in a cap table before an equity round?
There's no strict rule, but the practical convention is not to exceed 15 to 20% cumulative dilution in BSA Air before your first Seed. Beyond that, the VC balks and asks for a renegotiation first.
How do I explain a BSA Air to a VC looking at my cap table?
Present your cap table fully diluted, with the BSA Air already converted in a "Seed valuation = cap" scenario. The VC sees clearly the Air BAs' % post-conversion. More honest than a 100% founder cap table that hides €200K of commitment.
Do I need to declare the BSA Air in accounting?
Yes. The BSA Air is a security recorded in the share transfer register. The tax treatment (IR-PME in particular) only applies at conversion under certain conditions, not at the subscription of the BSA Air itself. Your accountant and your lawyer need to be aligned before signing.
