---
schema_version: "secwatch.filing_event.v1"
accession: "0001213900-26-093966"
form_type: "8-K"
ticker: "ARKB"
cik: "0001869699"
company_name: "Ark 21Shares Bitcoin ETF"
filed_at: "2026-08-26T20:11:51+00:00"
generated_at: "2026-08-26T20:13:06.202816+00:00"
event_type: "other_material"
sentiment: "neutral"
materiality_score: 0.4
calibrated_materiality_score: 0.4
confidence: "high"
source: SEC EDGAR
---

# ARK 21Shares Bitcoin ETF switches benchmark to FTSE Bitcoin Index, changes sponsor fee timing

## Summary
- Effective Aug 27, 2026, Trust will value shares and calculate NAV using FTSE Bitcoin Index, replacing CME CF Bitcoin Reference Rate - NY Variant.
- Sponsor fee payment changes from weekly to at least quarterly in arrears, payable in bitcoin, per Amendment No. 1 to Sponsor Agreement.
- Second Amended and Restated Trust Agreement dated Aug 26, 2026 reflects benchmark change and fee timing; other changes ministerial.
- Benchmark Licensing Agreement with FTSE International Limited dated Aug 20, 2026; one-year initial term, auto-renewal.
- Prior notice of termination of CF Benchmarks license given June 30, 2026, effective Aug 31, 2026.

## SEC filing metadata
- accession: 0001213900-26-093966
- form_type: 8-K
- ticker: ARKB
- cik: 0001869699
- company_name: Ark 21Shares Bitcoin ETF
- filed_at: 2026-08-26T20:11:51+00:00
- event_type: other_material
- sentiment: neutral
- materiality_score: 0.4
- calibrated_materiality_score: 0.4
- confidence: high
- sec_items: 1.01, 5.03, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1869699/000121390026093966/0001213900-26-093966-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1869699/000121390026093966/ea0303132-8k_ark21shares.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001213900-26-093966
- JSON: https://secwatch.observer/filing/0001213900-26-093966.json
- Plain text: https://secwatch.observer/filing/0001213900-26-093966.txt

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.