GBTC vs IBIT: Who really manages Bitcoin and what are the conditions for hosting?

For BlackRock's iShares Bitcoin Trust (IBIT), its custody arrangements are public record: According to a Form 8-K disclosure filed with the Securities and Exchange Commission (SEC) on April 7, 2025, BlackRock Fund Advisors signed a master custody service agreement to add Anchorage Digital Bank N.A. As the secondary custodian, Coinbase remains the main holder of Bitcoin in the trust.

For the Gray Scale Bitcoin Trust (GBTC), no similar filing document appears in the evidence collected for this page. The only basis for claiming that GBTC uses Coinbase custody trusts comes from the third-party ETF comparison tool Spark Money, which does not cite any filing documents as support.

Actual content of the Spot Bitcoin ETF Custody Agreement

Spot Bitcoin ETF does not hold futures or derivatives. It holds actual bitcoins and must physically secure the private key that controls those bitcoins. The entity is the custodian, and the agreement between the fund initiator and the custodian usually clarifies how the private key is stored, the applicable insurance coverage, and how to handle it in marginal situations such as blockchain forking.

According to reports, the April 2025 IBIT filing document is a useful example of the content of such an agreement. The agreement requires Anchorage to use cold storage of all private keys, maintain insurance coverage, and comply with terms regarding blockchain forking and liability. Anchorage is a federally chartered digital asset bank supervised by the Office of the Comptroller of the Currency, a detail that is believed to be relevant to the trust's compliance status.

Crucially, this is allegedly not a transfer of trusteeship. At the time of filing, Coinbase remained fully responsible for IBIT's current custody functions, and no bitcoins had been transferred to Anchorage. The report described Anchorage's role as a "standby" designed to achieve operational redundancy rather than being put into immediate use. The fee arrangement, structure and investment goals of the trust have not changed.

Common Misunderstandings

A filing for a new second custodian can easily be misinterpreted as a filing for transferring bitcoins. But this is not the case. According to reports on Form 8-K, Anchorage was introduced as a contract backup, not an active holder. BlackRock's public description of the move links it to risk mitigation and long-term operational redundancy, rather than any dissatisfaction with Coinbase.

Known and unknown on GBTC custody

Spark Money's comparison table shows that Coinbase Custody Trust is the custodian of 8 of the 11 original spot Bitcoin ETFs, and through the exclusion method, GBTC will be included in this group because Spark Money separately pointed out that Fidelity's FBTC is the only major fund that does not rely on Coinbase but uses Fidelity digital assets. Spark Money also pointed out that BRRR has added BitGo Trust Company to tie it with Coinbase, while ARKB and HODL have adopted a multi-custodian model. In the evidence collected on this page, none of these custody statements is attributed to any specific SEC filing, prospectus, or other major document. They should be viewed as statements from comparison and marketing tools, rather than as confirmed facts like IBIT's Form 8-K.

This is important because the two funds are not symmetrical in terms of reader-verifiable information. IBIT's custody structure can be traced to a dated regulatory filing containing specific contract terms. The hosting structure of GBTC can only be traced back to the summary table of the aggregator, and there is no equally referenced source.

Broader concentration issues

Spark Money described Coinbase's role in most of the original 11 funds as a concentration risk and said multiple issuers have responded through multiple custodian arrangements: IBIT uses Coinbase and Anchorage, BRRR uses Coinbase and BitGo, and ARKB and HODL are also described as multiple custodians. If accurate, the primary custody rights of most of the approximately US$91 billion in total assets of the U.S. spot Bitcoin ETF as of March 2026 reported by Spark Money will be concentrated in one company. However, this number and the number of custodians behind it in this collection of evidence come only from the Spark Money family, and the statement of "8 out of 11" is not supported by the SEC filing.

Spark Money also describes that all spot Bitcoin ETFs (including GBTC and IBIT) use a grantor trust structure, hold physical bitcoin, and settle authorized participants 'transactions in cash rather than in kind, which allegedly introduces small tracking errors with the spot price. This is presented as an industry-wide structural feature rather than a situation unique to a particular fund.

Background to the gap between scale and cost

Custody issues coexist with fees and size gaps that have been recorded since the first month of trading between the two funds. According to reports, as of May 28, 2024, IBIT held more than US$20 billion in assets and 288,670 bitcoins, exceeding GBTC's US$19.7 billion in assets and 287,450 bitcoins; On the reported Tuesday, GBTC experienced an outflow of US$105 million, while IBIT increased by more than US$100 million, followed closely by Fidelity's Bitcoin ETF with US$11 billion in assets. Bloomberg's report on the same incident also described IBIT surpassing GBTC to become the world's largest Bitcoin ETF;CoinDesk's market column that day also marked this turning point as a market event. Only these titles are quoted here, not the main text, because the original article text cannot be used for verification.

According to Spark Money, the gap has widened by March 2026. IBIT has a rate of 0.25% and assets of approximately US$70.6 billion; while GBTC has a rate of 1.50% and assets of approximately US$14.9 billion. Spark Money also reported that all 11 original spot Bitcoin ETFs together attracted a net inflow of more than US$56 billion in the first year, while the independent low-rate fund launched on July 31, 2024-Gray Bitcoin Mini Trust injected approximately 10% of GBTC's Bitcoin holdings as seed assets.

What this page cannot tell

This page cannot identify the custodian of GBTC from the grayscale SEC filing document. The only evidence collected claims to come from Spark Money, a comparison and marketing tool that does not mention any underlying documents, so the statement is reported here as unconfirmed information rather than fact.

The hosting details of IBIT are based solely on reports of the April 7, 2025 filing. Any subsequent changes to the custodian, including whether Anchorage has moved from standby to active use, will not appear on this page.

Spark Money's asset management scale and expense data are related to the March 2026 reference point in the article, but the page itself has no clear release date and is a comparison tool rather than a newsroom. The numbers are considered unaudited here and are not attributed to any major filing documents.

This page does not independently verify the custody terms described by Spark Money for its funds, including BRRR, ARKB, HODL, and FBTC. These statements are here repeated as statements from a single source rather than confirmed facts.

Finally, none of the insurance, indemnity or forking terms applicable in the GBTC escrow arrangements, if any, are covered in the evidence collected on this page. Whether Gray has plans for alternate or multi-custodian structures equivalent to IBIT is also unknown from this evidence.

Source

Each of the above facts is attributed to one of the above reports. If there are differences, the article has explained them.