Who Custodies IBIT? BlackRock's Bitcoin Custodian, Explained

IBIT, BlackRock's iShares Bitcoin Trust, holds its bitcoin with Coinbase Custody Trust Company, which the fund's prospectus names as its Bitcoin Custodian and which keeps the bitcoin in cold storage. Anchorage Digital Bank is named as an additional custodian, but BlackRock has stated it has no plans to move bitcoin there. A smaller trading balance sits with Coinbase, Inc. in omnibus wallets. IBIT shareholders own shares in the trust, not the bitcoin itself.

The iShares Bitcoin Trust held $63.7 billion in net assets as of September 18, 2026, which makes it the largest spot bitcoin ETF in the United States. Almost all of that bitcoin sits with one custodian. The prospectus states it directly: "Coinbase Custody Trust Company, LLC, the 'Bitcoin Custodian' is the custodian for the Trust's bitcoin holdings." That is not a criticism of Coinbase Custody. It is a fact about how the fund is built, and it is worth understanding if IBIT is a meaningful part of your bitcoin exposure.

The Two Balances Inside IBIT

IBIT's bitcoin sits in two places, and the prospectus treats them differently.

The Vault Balance is the large majority of the fund. Coinbase Custody holds it in cold storage, in accounts that the prospectus says are segregated from the custodian's own assets and from the assets of its other customers.

The Trading Balance is the bitcoin the fund keeps available for buying and selling. It sits with Coinbase, Inc., which serves as the fund's Prime Execution Agent, and the prospectus describes it as held "across a combination of omnibus cold wallets, omnibus 'hot wallets'" and omnibus accounts on trading venues. Omnibus means the bitcoin is pooled with that of other customers. This distinction explains why some answers online describe IBIT's custodian as "Coinbase Prime." That describes the trading side. The vault is Coinbase Custody. Both are Coinbase entities.

Anchorage, the Additional Custodian

The prospectus names Anchorage Digital Bank as an "Additional Bitcoin Custodian," meaning an available alternative. As of the July 2025 prospectus, BlackRock stated that "the Sponsor has no plans to move any of the Trust's bitcoin to the Additional Bitcoin Custodian, though such plans are subject to ongoing review." In practice, Anchorage is a backup that exists on paper rather than a second place where IBIT's bitcoin is held today.

What an IBIT Share Is, and What It Is Not

An IBIT share is a share in a trust that holds bitcoin. It is not bitcoin, and an individual holder cannot exchange it for bitcoin. The prospectus is explicit: "Except when aggregated in Baskets, Shares are not redeemable securities. Baskets are only redeemable by Authorized Participants." Authorized Participants are large broker-dealers. An individual who wants out sells shares for dollars. That tradeoff is deliberate, and for many holders it is the right one. The ETF delivers bitcoin's price inside a brokerage account or retirement plan, with nothing to manage.

Insurance and FDIC Coverage

Not in the way a bank deposit is. The prospectus states that "the Shares are not insured or guaranteed by the Federal Deposit Insurance Corporation ('FDIC') or any other governmental agency." It does not state that the custodian's own insurance covers the trust's bitcoin. If insurance matters to your decision, ask your broker or the sponsor directly what, if anything, covers the fund's holdings.

Why the Custodian Matters More Than It Looks

Coinbase Custody is not only IBIT's custodian. By recent estimates, a single custodian underpins more than 80 percent of US spot bitcoin ETF assets, and it is widely reported to be Coinbase Custody. That concentration is covered in detail in Who Custodies Bitcoin ETFs?. The point is not that anything is wrong today. It is that when most of a market sits with one provider, a problem at that provider stops being one fund's problem and becomes the market's. An IBIT holder has no ability to change that arrangement, only to decide whether to hold it.

What IBIT Costs

The sponsor fee is 0.25% a year, charged on the value of the fund. On a $1 million position that is roughly $2,500 a year, and because the fee is a percentage, the dollar cost rises as bitcoin's price rises.

Who IBIT Fits

IBIT fits someone who wants bitcoin's price inside a brokerage account, a 401(k), or an IRA they already have, who will never need to move the bitcoin itself, and who is comfortable with a single custodian holding it. Plenty of long-term holders keep an ETF position for exactly those reasons, often alongside bitcoin they hold directly for the longer term.

For Holders Who Chose IBIT to Stop Managing Keys

Some long-time holders have moved bitcoin out of self-custody and into an ETF for one reason: they no longer want to manage keys. Hardware wallets, seed phrases, firmware updates, and a recovery plan their family could actually follow had become more burden than they wanted to carry. That is a reasonable decision, and the ETF does remove the burden.

It removes it by replacing the bitcoin with a share. Multi-Institution Custody removes the same burden while you keep the bitcoin.

With Onramp's Multi-Institution Custody, three institutions protect your bitcoin: Onramp (US), BitGo Trust (US), and CoinCover (UK). No one of them can lose it, move it, or use it, and nothing moves without your permission. It takes two of three institutions to move your bitcoin, and there are no hardware wallets, seed phrases, backups, or PINs for you to manage. Secured by three. Controlled by you.

For someone weighing the two, the differences are concrete:

• What you own. IBIT: Shares in a trust; Onramp Multi-Institution Custody: Bitcoin, in a vault in your own name
• Who holds it. IBIT: One custodian (Coinbase Custody), with a trading balance in omnibus wallets; Onramp Multi-Institution Custody: Three independent institutions; no single one can move it
• Keys you manage. IBIT: None; Onramp Multi-Institution Custody: None
• Verify your holdings. IBIT: Fund disclosures; Onramp Multi-Institution Custody: On-chain, whenever you want to look
• Inheritance. IBIT: Shares pass through your brokerage account; Onramp Multi-Institution Custody: Bitcoin passes to named beneficiaries, with a real person guiding your family
• Retirement accounts. IBIT: Held in a brokerage IRA as a fund; Onramp Multi-Institution Custody: Onramp IRA holds bitcoin itself, in the same custody model
• Cost. IBIT: 0.25% a year, rising with bitcoin's price; Onramp Multi-Institution Custody: Core starts at $2,400 a year flat, up to 10 bitcoin

Two practical points are worth knowing before choosing. First, moving bitcoin you already hold into IBIT typically means selling it and buying shares, and a sale may be a taxable event. Bitcoin can move into a vault as bitcoin. Second, on cost the two are close at around $1 million, but the ETF fee grows with bitcoin's price while Onramp's Core tiers are set in bitcoin terms. Neither is universally cheaper, and the right comparison depends on your position and how long you intend to hold it.

For how ETF holders typically make the move, see Bitcoin ETF Alternatives.

Frequently Asked Questions

Who is IBIT's bitcoin custodian?

Coinbase Custody Trust Company, LLC. The prospectus names it the Bitcoin Custodian. Anchorage Digital Bank is named as an additional, available custodian, and BlackRock has said it has no current plans to move bitcoin there.

Does BlackRock hold IBIT's bitcoin?

No. BlackRock sponsors the trust. The bitcoin is held by Coinbase Custody in cold storage, with a trading balance at Coinbase, Inc.

Can I redeem IBIT shares for bitcoin?

Not as an individual. Only Authorized Participants can redeem shares, and only in large blocks called Baskets. Individual holders sell shares for dollars.

Is the bitcoin in IBIT held separately from other customers' bitcoin?

The Vault Balance at Coinbase Custody is held in segregated accounts, according to the prospectus. The Trading Balance at Coinbase, Inc. is held in omnibus wallets and accounts, which pool customers' bitcoin.

Is IBIT FDIC insured?

No. The prospectus states that the shares are not insured or guaranteed by the FDIC or any other governmental agency.

Sources (checked September 21, 2026):

• iShares Bitcoin Trust prospectus, ishares.com (Bitcoin Custodian and Additional Bitcoin Custodian roles; redemption)
• IBIT prospectus Form 424B3, July 31, 2025, sec.gov (Trading Balance, omnibus wallets, no plans to move to Anchorage, FDIC)
• iShares IBIT product page (sponsor fee 0.25%, net assets $63,709,190,713 as of September 18, 2026, inception January 5, 2024)