U.S. spot bitcoin ETF net flows reach $2.73 billion from September 1-28, 2026, according to data from Farside Investors. August ended at 3.52 billion. But September is not like August: 2.42 billion, or 88% of the total, arrived in six sessions, from September 21 to 28. Tremplin.io reconstructed the two months session by session to show it.
In brief
- +$2.73 billion: net flows of bitcoin ETFs from September 1 to 28, over 19 sessions (Farside Investors, TFTC).
- +313.5 million only over the first 13 sessions, then +2.42 billion over the next 6.
- +3.52 billion in August, over 21 sessions, including 16 positive.
What do bitcoin ETF flows measure?
A bitcoin spot ETF is an exchange-traded fund that holds bitcoin. When investors buy shares, the fund creates new shares and buys bitcoin. The net flow is the difference between these creations and redemptions, in dollars, for a session. Tremplin.io had followed the moment when the 2026 flows returned to green.
The figures in this article add up the daily flows of all US-listed spot bitcoin ETFs. From September 10 to 28, they come from Farside Investors table. For August and the beginning of September, they have just TFTCwhich compiles the same declared streams. The two series agree within 0.1 million on common dates.
How does September compare to August?
August rose steadily. Sixteen sessions out of 21 were positive. The highest, on August 20, brought in $606.3 million. The worst, on August 28, cost 201.8 million.
September bitcoin ETF flows followed a different trajectory. After thirteen sessions, the total did not exceed $313.5 million. On September 15, funds lost 450.4 million in one session, the largest outflow in two months. That day, the American Senate rejected by 49 votes to 50 the procedure which was to advance the CLARITY Act, according to CNBC. The data does not say whether the two facts are linked.
Then the curve straightened out. On September 21, ETFs received $999 million, their best session in two months. The next five sessions added 1.42 billion.
| Indicator | August 2026 | September 2026 (to 28) |
| Cumulative net flows | +$3.52 billion | +$2.73 billion |
| Sessions | 21 | 19 |
| Positive sessions | 16 | 12 |
| Best session | +$606.3 million (August 20) | +$999.0M (September 21) |
| Worst session | −$201.8 million (August 28) | −$450.4 million (September 15) |
Bitcoin ETF flows throughout 2026
The balance for 2026 has become positive again. As of mid-July, bitcoin ETFs showed $5.8 billion in net outflows since January, according to SoSoValue data. As of September 24, the year-to-date total reached approximately 886.8 million entries, according to Decrypt, taken over by Yahoo Finance. Since their launch in January 2024, these funds have raised a net $58 billion, according to the same source.
What these numbers don’t say
Not all aggregators publish the same amounts. As of September 21, Farside has $999 million, and Bitcoin Treasuries shows 1.41 billion. For September 15, the difference goes from −450.4 to −198.1 million. Collection methods and collection times differ. Comparing figures from different sources therefore distorts the reading.
A net flow also doesn’t tell you who is buying, or why. It measures demand for ETF shares in the United States, in dollars. It does not measure purchases on crypto platforms or demand outside the United States. To choose between an ETF and bitcoin held directly, our comparison between spot ETF and bitcoin details the differences.
September bitcoin ETF flows end at $2.65 billion, up from $3.52 billion in August, according to Farside. The last session, on September 30, recorded 148.7 million outflows, including 125.6 million for Fidelity’s FBTC fund
Maximize your Tremplin.io experience with our ‘Read to Earn’ program! For every article you read, earn points and access exclusive rewards. Sign up now and start earning benefits.
