U.S. spot Bitcoin exchange-traded funds recorded $998.95 million in net inflows on Monday, their strongest single-day result since October 2025, according to SoSoValue. Net inflows measure new capital entering the funds, which hold bitcoin directly and can be bought and sold through standard brokerage accounts. The surge came one week after the funds posted their smallest weekly net inflow on record.

BlackRock's IBIT led Monday's intake with $381.37 million. ARK 21Shares' ARKB attracted $289.12 million, while Fidelity's FBTC brought in $238.84 million. Morgan Stanley's MSBT added $61.67 million, and Bitwise's BITB recorded $21.56 million. Grayscale's two funds each received single-digit millions, while VanEck's HODL and Valkyrie's BRRR reported no inflows.

The daily result was a sharp from the previous week. For the week ending September 18, the funds finished with only $6.2 million in net inflows, their smallest weekly total across 141 weeks of trading. Bloomberg Intelligence analyst Eric Balchunas described Monday's figure as the largest single-day inflow since last October. The swing — from the weakest week in the funds' history to nearly $1 billion in a single session — shows how quickly participation in the products can shift from one reporting period to the next.

Bitcoin's rally also pushed its price above an estimated average cost basis of $81,722 for holders of U.S. spot Bitcoin ETFs. Cost-basis estimates of this kind track the average price at which fund investors accumulated their positions, marking the level at which the typical holder's position moves between loss and gain. That put the average fund holder back in profit for the first time since January, according to James Seyffart, Balchunas' colleague at Bloomberg Intelligence. Bitcoin was trading near $85,900 at the time, approximately 5% above the estimated cost basis.

Seyffart wrote on X:

NEW: The average Bitcoin ETF Holder is back above water for the first time since January. The rally this morning has bitcoin:native above our estimated ETF cost basis of $81,722 per coin. h/t @EricBalchunas pic.twitter.com/h21zuvTxj6 — James Seyffart (@JSeyff) September 21, 2026

David Wachsman, president of Hawkeye Digital, said the cost-basis milestone could be more significant than the headline flow figure. Investors holding positions at a loss "often sell the first chance they get to break even," he said, meaning that much of this year's demand has had to absorb that potential selling pressure. With the average buyer back in profit, the balance between new institutional demand and investors participating in the recent rally may become clearer.

Trading activity was less pronounced. The funds recorded approximately $4.5 billion in turnover, slightly below the $4.6 billion traded on Friday. Seyffart said the figure was not especially high relative to the size of Bitcoin's price move. Balchunas said it was elevated compared with stock and gold ETFs and noted that IBIT ranked at or near the top 10 ETFs by trading volume.

Balchunas also cautioned that reported flows for a given session generally reflect activity from the previous trading day. Monday's total likely captured buying from Friday rather than Monday itself, he said, meaning the funds' response to Monday's price move had yet to appear in the flow data. Because of that one-session lag, the coming days of flow reports will show how buyers reacted to Monday's move itself.

Cumulative net inflows since the funds launched have reached $56.16 billion. Their total holdings stand at $110.14 billion, equivalent to 6.30% of Bitcoin's market capitalization — a scale that has made the products' daily flow figures a standard reference point for tracking institutional participation in bitcoin.

"Bitcoin's recent recovery toward the $86K–$87K range is being supported by renewed institutional demand, stronger spot ETF inflows and evolving US regulatory developments," said Vikas Gupta, Bybit's country manager for India. He said the market had held up despite the Federal Reserve's rate hike and the failure of the Clarity Act in the Senate, suggesting that monetary policy was not the only factor influencing market conditions.

Source: Decrypt