Block said on 8 September it has applied to the Office of the Comptroller of the Currency to establish Builders Bank & Trust, N.A., an uninsured national trust bank for bitcoin and stablecoin custody. The release says it "would not accept deposits or make loans" — which removes net interest income, leaving fees for holding other people's assets — and that it "would not commence operations unless and until it receives the required regulatory approvals."
Block already does the job. Its June-quarter filing says it "allows its Cash App customers to store their bitcoin in the Company's digital wallets free of charge," holding the keys and the recordkeeping itself. So the question is not what a custody bank could earn but who it is for, and the last number Block published answers it. Under the SEC's old safeguarding rule it disclosed $1.41bn of customer bitcoin at 30 September 2024; the rule was rescinded in January 2025 and Block now recognises no such amount, so that stale figure is the only anchor anyone has. At iShares' published 0.25% sponsor fee it would yield about $3.5M a year — 1.2% of the roughly $288M annual gross profit run rate of Block's Bitcoin Ecosystem line, which turned $1,894M of revenue into $72M of gross profit in the June 2026 quarter.
A charter this small against the existing book is not a Cash App product. It is a regulated wrapper aimed at institutions who need a supervisor's name — which is checkable the moment Block publishes a fee schedule or an assets-under-custody target, and unfalsifiable until it does.
The application, the two quoted phrases and the 8 September date are from Block's announcement; the free-custody quote, the $1.41bn safeguarding balance at 30 September 2024 and the derecognition are from Block's own filings; the June-quarter segment figures are as reported, captured in our June-quarter notes. The 0.25% rate is iShares' published sponsor fee applied to a book Block has not updated in nearly two years — the yield is R40 arithmetic on a stale anchor, not a forecast.
