Startup Money · Future equity financing
SAFEs, ASAs, convertible loans and BSA AIR all postpone some parts of a financing deal. But they are not legally interchangeable—and a cap that sounds generous can hide meaningful dilution.
Founder finance · Illustrative, source-backed · 14 October 2026
A pricing decision deferred
The attraction of an early convertible financing instrument is speed: the startup gets money before it is ready to negotiate a full priced-equity round. The investment document nevertheless determines how much ownership may be issued later and what happens if the expected round is delayed.
Founders should translate any proposed cap, discount, interest, maturity or conversion condition into a future fully diluted ownership scenario—and establish whether a different legal structure would suit the country of incorporation and the investors involved.
Terminology is not jurisdiction-neutral
These structures share the commercial ambition of raising capital before a fully negotiated new-money valuation, but their documentation, investor rights and tax effects differ. The comparisons below are descriptive, not a ranking.
Contractual right to later equity
When equity appears: Automatically becomes equity in a qualifying priced round under the SAFE's provisions.
Review: Post-money valuation cap, discounts or MFN, total SAFEs, equity financing, pro-rata side letters and the new option pool.
Advance payment for future shares
When equity appears: Shares issued on terms and by the longstop specified in the agreement. Examine tax-relief eligibility separately.
Review: Irrevocability, refundability, interest, longstop and investor/company SEIS/EIS criteria; not automatically a debt instrument.
Contractual loan with a possible or required equity conversion
When equity appears: Conversion into GmbH equity under the loan agreement and applicable company-law formalities.
Review: Maturity, interest, subordination, trigger, cap/discount, insolvency ranking and whether programme incentives apply.
Warrant-based future equity subscription
When equity appears: Warrants are exercised into newly subscribed shares according to the agreement and triggering event.
Review: Trigger events, valuation floor/cap, discount, share approvals and the legal/tax consequences of warrant issuance.
In UK SEIS advance-assurance cases, HMRC expects an ASA not to behave like a loan and generally expects a share-issuance longstop within six months. That six-month guidance concerns HMRC's advance-assurance process; it is not a universal legal maximum for every ASA. German INVEST eligibility similarly has programme-specific restrictions that must not be presented as laws applying to all convertible loans.
Learn the U.S. post-money cap mechanics
The post-money valuation cap is designed to make the proportion of equity sold clearer. In a cap-binding U.S. YC post-money SAFE, the initial ownership implied by the cap is approximately the amount invested divided by the cap. This percentage is calculated before the future priced round; the new investor and any new pool can dilute the SAFE holder later.
Step 1
SAFE cash ÷ post-money valuation cap
One $500k SAFE on $5m post-money cap implies 10% ownership before the later financing, in the binding-cap case.
Step 2
New cash ÷ (pre-money + new cash)
At $9m fully diluted pre-money with $3m new cash, the new investor gets 25% post-financing.
Step 3
Old owners × pool survival × round survival
New pre-money pool shares and the financing dilute both founders and existing SAFE investors.
The exact YC contract includes definitions of company capitalization and safe-price versus standard new-money-price conversion. If the round values the company at or below the cap, the cap might not govern conversion. The interactive model below rejects such cases rather than guessing.
Interactive exercise · U.S. post-money valuation-cap SAFE only
Start with one fictional founder-owned company, issue one post-money valuation-cap SAFE, then simulate a new priced round and an additional pre-money hiring pool. Every result is calculated in your browser.
The fictional company begins with 100% founder-held common equity and no existing options or other securities.
The option pool here is an additional, newly allocated pool before the priced round. It dilutes both founders and converted SAFE investors, not the new priced-round investors. It is modeled as issued/allocated ownership for teaching; employee grants and vesting are not modeled.
2. The ownership math
SAFE investor · before round
10.00%
Founder · before round
90.00%
After SAFE conversion, new pool and the priced round
SAFE ownership before round = SAFE investment ÷ post-money cap. New priced investor ownership = new cash ÷ (priced pre-money + new cash). Pool and later financing dilute existing owners as specified.
Modeled post-money round valuation: $12,000,000. Fully diluted sum: 100.00%.
Strict teaching scope: this is not the share count from a live financing. It assumes the cap is binding, the round valuation is stated for the fully diluted pre-round company, and just one cap-only post-money SAFE. It excludes pre-money SAFEs, discount/MFN terms, other SAFEs, existing options, notes, pro-rata side letters, investor preferences, debt and tax effects. The official Y Combinator conversion calculator supports more complete SAFE structures.
Worked fictional example
A founder owns 100% before a $500,000 U.S. post-money SAFE with a $5m valuation cap. The SAFE's implied 10% stake leaves 90% for the founder immediately before the priced round. If the company then raises $3m on an assumed $9m fully diluted pre-money valuation, the new investors own 25% of the post-money company.
Without an additional pool
SAFE investor: 7.5% · New priced investor: 25%. Their amounts sum to 100% in this deliberately simple scenario.
With a 10% NEW pre-money pool
SAFE investor: 6.75% · New employee pool: 7.5% · Priced investor: 25%. The pool is 10% before the round and 7.5% after the new investment.
These are illustrative fully diluted percentages under the exact assumptions described in the simulator, not a substitute for the YC share-issuance calculator or a cap-table certification. The effect can differ materially with more SAFEs, outstanding options, pro-rata side letters or a price below the cap.
Founder diligence
A share subscription, future equity agreement, advanced share payment, debt or warrant? Never infer the legal category merely from the marketing name.
Find the exact cap, discount, interest, warrants, seniority and any other economic rights. A cap is not always the eventual financing valuation.
Understand the financing trigger, longstop, maturity, exercise period, minimum round size and what happens if the anticipated priced round never occurs.
Count all promised equity, issued options, outstanding SAFEs, warrants, bridge notes and likely option-pool expansions before telling founders their percentage.
Timing matters. A new pre-money option pool can reduce founders and converted SAFE holders before new money invests; a signed post-money cap can protect a negotiated portion of ownership.
Review priority, repayment rights, change-of-control treatment, liquidation preferences, insolvency subordination and local tax exposure.
Assignment · Founder finance
Analyse three fictional early-stage ventures: a Delaware C-corporation, a UK company seeking SEIS/EIS, and a German GmbH. For each venture, propose an appropriate funding-structure discussion, list the critical terms to verify, identify the source of future dilution and produce three questions for qualified local counsel. Explain why the same numerical cap can represent different obligations in different instruments.
Use the SAFE calculator for a hypothetical U.S. cap-binding example only. Then contrast how a UK ASA, German Wandeldarlehen and French BSA AIR would have to be analysed differently. You will receive more credit for identifying what you cannot determine than for inventing a clean but unsupported percentage.
A future-equity conversion tells you how many shares are created—not necessarily how proceeds are allocated at exit. Continue with our term-sheet decision lab to understand liquidation preferences, founder incentives and control rights.
Open the term-sheet simulatorThe official Y Combinator SAFE documentation and calculator govern the example's economic definitions. HMRC's UK guidance is specific to tax relief and advance assurance; the German ministry's convertible-loan conditions are specific to its INVEST funding programme. French resources explain BSA AIR warrants but do not replace jurisdiction-specific legal advice. All quoted numerical scenarios are hypothetical and last reviewed 14 October 2026.
This guide is educational, not a recommendation to issue, invest through or convert any security. A qualified local lawyer and tax adviser should review actual financing documents.