Answer 7 questions about how you store your bitcoin. The Durability Test gives you a score and tells you what to do first to protect it.
Your answers stay in your browser. Casa does not see or save them.
We never ask for your seed phrase, your balance or your name.
This is your estimate. It is not a forecast.
IBIT fees in 20 years
$142,332
The fee is a percentage of your balance. When your balance grows, the fee grows. The fee is $1,438 in year 1 and $19,508 in year 20.
Casa Premium costs $2,100 each year. This price does not change with your balance. The fund fee is more than this price from year 4.
“The amount of bitcoin represented by each Share will decrease over the life of the Trust due to the sales of bitcoin necessary to pay the Sponsor’s Fee.”
IBIT prospectus
The IBIT sponsor fee is 0.25% of your balance each year (source: iShares fund page, October 1, 2026). The Casa Premium price is the current list price. This calculator applies the fee 1 time each year. Funds apply it each day. This is an example. It is not investment advice.
We found no US spot bitcoin ETF that lost bitcoin at its custodian. But the structure of a fund has risks.
The IBIT prospectus says “Individual Shares will not be redeemed by the Trust.” Only authorized participants can exchange shares for bitcoin. They are registered broker-dealers, and they exchange 40,000 shares at a time. Before GBTC became an ETF, the price of its shares was as much as 49% less than the value of its bitcoin.
IBIT prospectusGrayscale 2023 annual reportCoinbase is the custodian for most US spot bitcoin funds. IBIT is one of them. Coinbase says that it holds more than 80% of US bitcoin and ether ETF assets.
Coinbase shareholder letter, Q4 2025The IBIT custodian has crime insurance of up to $320 million. All its customers share this insurance. The prospectus says that this amount “may be substantially lower than the assets of the Trust.” The trust and its sponsor do not insure the bitcoin.
IBIT prospectusA court can decide that the bitcoin is part of the property of a bankrupt custodian. The prospectus says that this can cause “protracted litigation”. It also says that the trust can get back “only a fraction of the Trust’s property.”
IBIT prospectusCompanies that hold bitcoin for customers failed in the past. Some of them were regulated. Prime Trust was a regulated trust company in Nevada. In 2023 it did not pay withdrawals, and it went bankrupt. These are the total losses at exchanges, lenders and custodians.
See all 154 incidents and their sourcesThe amounts are from the time of each incident. Some companies repaid their customers later. The full list shows which companies did.
$28.5B
This is the total that was lost, stolen or frozen at exchanges, lenders and custodial wallets since 2011. Amounts are in US dollars at the time of each incident.
Mt. Gox stopped withdrawals 3 weeks before it filed for bankruptcy. Celsius, Voyager and FTX also stopped withdrawals days or weeks before they filed. When the public learns about the problem, customers can no longer withdraw.
Reuters on Mt. GoxThe Block on CelsiusThe Block on VoyagerMt. Gox customers started to get bitcoin back in July 2024. That was 10 years after the exchange failed. QuadrigaCX made its first payment after 4 years. Customers got approximately 13 cents for each dollar.
Mt. Gox trusteeCoinDesk on QuadrigaCXFTX repaid its customers in US dollars, plus interest. It used the value of each claim on the day of the bankruptcy in November 2022. Customers did not get their bitcoin back.
CoinDesk on FTX repaymentsBybit lost $1.5 billion in 2025. Bitget lost $387.5 million in 2026. Each company paid for the loss with its own funds. Customers are repaid only if the company has sufficient funds.
FBI on BybitChainalysis on BitgetSee all 154 incidents and their sourcesThe amounts are from the time of each incident. Some companies repaid their customers later. The full list shows which companies did.
Then you do not control your bitcoin, because the company or the fund holds the keys. An exchange can freeze your account. An exchange or the custodian of a fund can fail, and you can lose your bitcoin. A fund also charges a fee every year, and the fee grows with your bitcoin.
$28.5 billion
lost, stolen or frozen at exchanges, lenders and custodial wallets since 2011
$142,332
in fees in 20 years, for $500,000 in a fund
This example uses a 0.25% fee and 15% growth each year.
After you complete a step, do the test again to see your new score.
Your protection from each risk
The test has 7 questions. Each question covers 1 risk. Each answer gives you some or all of the points for that risk. The answer “I do not know” gives 0 points, because it is a risk not to know.
Your browser calculates the score. Your answers stay in your browser, and Casa does not see or save them. Your browser keeps your last score, so the test can show your progress next time. Casa never asks for your seed phrase. The score is an estimate for education. It is not a security audit.
For Level IV, your keys and backups must be in different locations. You must also be able to recover if you lose 1 signing device and its seed phrase. For Level V, your inheritance plan must also have a successful test.
