Write an option
Writing earns you BTC upfront. You pick a price target BTC has to stay below over a chosen window. If BTC stays at or below that strike at expiry, you keep your full collateral and the premium. If BTC ends above, you pay the buyer the percentage by which BTC exceeded your strike, in BTC, out of your collateral.
In a sharp move (BTC running well past your strike), the worst case is losing the full collateral you committed. That outcome is rare but possible, and it's what you're getting paid the premium to take on.
The write flow
The app walks you through four steps.
1. Pick when, and the price BTC should stay below
Choose a term and a strike (a percentage above the current BTC price).
The strike percentage is converted to a USD price the moment a buyer accepts, using the BTC/USD price at that moment.
Higher strikes are typically safer and earn less; lower strikes typically earn more but get hit more often. More on the trade-off in Write or Buy.
2. Set the amount
Choose how much BTC to back the offer with. This is your maximum exposure.
Offers can be filled by multiple buyers. A 1 BTC offer might be split into two fills, with each fill paying you premium proportionally. You can cancel any unfilled portion at any time.
3. Set the premium
Pick the premium you want to charge as a percentage of the offer size. The app shows the equivalent APY and your offer's competitiveness against other open offers at the same strike and term.
Lower premiums fill faster. Higher premiums earn more per fill but may not fill at all.
4. Review and confirm
The review screen shows strike, term, amount, premium, APY, competitiveness, and the platform fee. Slide to confirm and sign in your wallet.
How buyers pick your offer
For a given strike and term, your offer is ranked against other open offers by:
- Premium (lowest first). The cheapest offer for the strike fills first.
- Created at (oldest first) for ties. At the same premium, the offer created earlier gets matched first (FIFO).
- Size. Each buyer fills from one offer at a time. A buyer needing more size than the cheapest offer can fill will skip it and take the next offer big enough, even at a higher premium.
The competitiveness label on the premium step shows where you'd rank by premium. The "Largest" badge on your offer card appears when your offer is the biggest in the book. Even at a higher premium, you'll still capture buyers too big for cheaper offers.
Limits
- Minimum offer size: 0.0004 BTC (40,000 sats).
- Maximum offer size: 1 BTC.
- Up to 5 open offers per term.
What happens next
Your offer goes live and appears in Portfolio → Offers. Creating the offer does not lock your BTC, so your open offers can exceed your available balance. When that happens, each offer can only fill up to what's available, shown as Backed: X of Y (or Insufficient available balance if too low to fill at all).
When a buyer accepts (in whole or in part):
- The accepted amount of your BTC moves from available to locked.
- Your premium credits to your available balance immediately.
- The accepted portion appears in Portfolio → Active as a written option. Any remaining unfilled portion stays in Portfolio → Offers.
At expiry, the option settles automatically. Expiries land on the top of the hour: an offer accepted at 12:01 with a 7-day term expires at 13:00 seven days later.
- BTC closes at or below strike: your locked BTC unlocks. You keep the premium and the full collateral.
- BTC closes above strike: the buyer's profit is paid out from your locked BTC. Whatever's left unlocks back to you. You still keep the premium.
Worked example
You write 1 BTC at +10% strike for a 7-day term with a 2% premium. BTC is at $100,000 when a buyer accepts in full.
- Strike locks at $110,000.
- Your premium of 0.02 BTC credits immediately.
- 1 BTC moves into locked.
| BTC at expiry | % over strike | Your final position | Final position USD |
|---|---|---|---|
| $90,000 | n/a (under) | 1 BTC + 0.02 premium = 1.02 BTC | ~$91,800 |
| $100,000 | n/a (under) | 1 BTC + 0.02 premium = 1.02 BTC | ~$102,000 |
| $110,000 | 0% | 1 BTC + 0.02 premium = 1.02 BTC | ~$112,200 |
| $111,100 | 1% | ~0.99 BTC + 0.02 premium = ~1.01 BTC | ~$112,200 |
| $140,000 | 27% | ~0.73 BTC + 0.02 premium = ~0.75 BTC | ~$104,600 |
The further BTC runs above strike, the more of your collateral the buyer takes. You always keep the premium.