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HowShorted

How shorted is IONIS PHARMACEUTICALS INC? IONS

#446most shorted US stockof 3,805 ranked stocks, more shorted than 88%

12.57%
of shares outstanding reported short · settlement date 15 Sep 2026
vs previous report
−0.02
5 reports (~10 weeks)
+2.03
days to cover
5.20
Aggregate net short position time series for IONIS PHARMACEUTICALS INC

Markers along the chart's base: ▲ results announced (an 8-K reporting results was filed) ▲ quarterly or annual report filed. Dates are SEC filing dates; hover a point to see events since the previous settlement.

Days to cover

FINRA's own figure: reported shares short divided by the stock's average daily trading volume, published alongside each settlement. It expresses the short position in days of typical trading rather than as a percentage of the company; the two can move differently.

Aggregate net short position time series for IONIS PHARMACEUTICALS INC days to cover

Short interest around results

For each results announcement (an 8-K reporting results, by its SEC filing date), the FINRA settlement before it and the first one after. Settlements fall twice a month, so the two figures can sit up to a month apart and much else changes in between: this shows what was reported, not why.

Reported short interest before and after each results announcement
Results filedSettlement beforeSettlement afterChange
29 Jul 202612.13% 15 Jul 202612.92% 31 Jul 2026+0.79
29 Apr 20268.50% 15 Apr 20269.85% 30 Apr 2026+1.35
25 Feb 20269.56% 13 Feb 20269.46% 27 Feb 2026−0.10
12 Jan 20269.19% 31 Dec 20258.48% 15 Jan 2026−0.71
29 Oct 20258.59% 15 Oct 20257.82% 31 Oct 2025−0.77
30 Jul 20258.10% 15 Jul 20257.27% 31 Jul 2025−0.83
30 Apr 20259.15% 15 Apr 20259.59% 15 May 2025+0.44
19 Feb 20257.97% 14 Feb 20258.09% 28 Feb 2025+0.12

Fails to deliver

The SEC's fails-to-deliver figure for IONS: the aggregate net balance of shares that failed to be delivered at each settlement date, published by the SEC twice a month and shown here verbatim for the trailing window. A balance is not a daily flow, and a fail has many ordinary causes; the SEC says it cannot guarantee the accuracy of the data. See what fails to deliver are and the largest balances today.

Last balance on file
5,975
10 Sep 2026
Highest in window
134,554
1 Oct 2025
Days with a balance
120
Window
16 Sep 2025 to 14 Sep 2026
Aggregate net short position time series for IONIS PHARMACEUTICALS INC fails to deliver

Source: U.S. Securities and Exchange Commission, fails-to-deliver data (public domain). Only settlement days with a positive balance appear; the largest balance in the window was 135K shares.

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Sector: Healthcare

History

Full reported short interest history
Settlement dateShort %Change
15 Sep 202612.57%−0.02
31 Aug 202612.59%+0.01
14 Aug 202612.58%−0.34
31 Jul 202612.92%+0.79
15 Jul 202612.13%+1.59
30 Jun 202610.54%−0.20
15 Jun 202610.74%+0.46
29 May 202610.28%+0.55
15 May 20269.73%−0.12
30 Apr 20269.85%+1.35
15 Apr 20268.50%−0.35
31 Mar 20268.85%+0.24
13 Mar 20268.61%−0.85
27 Feb 20269.46%−0.10
13 Feb 20269.56%−0.03
30 Jan 20269.59%+1.11
15 Jan 20268.48%−0.71
31 Dec 20259.19%−0.74
15 Dec 20259.93%+0.28
28 Nov 20259.65%+0.87
14 Nov 20258.78%+0.96
31 Oct 20257.82%−0.77
15 Oct 20258.59%+0.89
30 Sep 20257.70%+0.19
15 Sep 20257.51%+0.92
29 Aug 20256.59%−0.18
15 Aug 20256.77%−0.50
31 Jul 20257.27%−0.83
15 Jul 20258.10%−0.78
30 Jun 20258.88%−0.06
13 Jun 20258.94%−0.38
30 May 20259.32%−0.27
15 May 20259.59%+0.40
30 Apr 20259.19%+0.04
15 Apr 20259.15%+0.76
31 Mar 20258.39%+0.33
14 Mar 20258.06%−0.03
28 Feb 20258.09%+0.12
14 Feb 20257.97%+0.29
31 Jan 20257.68%+1.19
15 Jan 20256.49%−0.41
31 Dec 20246.90%+0.23
13 Dec 20246.67%+0.05
29 Nov 20246.62%−0.38
15 Nov 20247.00%+0.20
31 Oct 20246.80%+0.05
15 Oct 20246.75%−0.45
30 Sep 20247.20%−0.06
13 Sep 20247.26%+0.31
30 Aug 20246.95%+0.18
15 Aug 20246.77%+0.30
31 Jul 20246.47%+0.05
15 Jul 20246.42%−0.10
28 Jun 20246.52%+0.59
14 Jun 20245.93%+0.04
31 May 20245.89%−0.02
15 May 20245.91%−0.19
30 Apr 20246.10%−0.55
15 Apr 20246.65%+0.01
28 Mar 20246.64%−0.10
15 Mar 20246.74%+0.39
29 Feb 20246.35%+0.03
15 Feb 20246.32%+0.43
31 Jan 20245.89%−0.06
12 Jan 20245.95%+0.20
29 Dec 20235.75%−0.22
15 Dec 20235.97%−0.79
30 Nov 20236.76%−0.03
15 Nov 20236.79%+0.03
31 Oct 20236.76%+0.39
13 Oct 20236.37%−0.12
29 Sep 20236.49%−0.05
15 Sep 20236.54%+0.06
31 Aug 20236.48%−0.25
15 Aug 20236.73%+0.29
31 Jul 20236.44%+0.25
14 Jul 20236.19%+0.16
30 Jun 20236.03%−0.05
15 Jun 20236.08%+1.52
31 May 20234.56%−0.41
15 May 20234.97%+0.06
28 Apr 20234.91%+0.04
14 Apr 20234.87%−0.33
31 Mar 20235.20%−0.19
15 Mar 20235.39%−0.36
28 Feb 20235.75%+0.47
15 Feb 20235.28%−0.48
31 Jan 20235.76%+0.03
13 Jan 20235.73%−0.38
30 Dec 20226.11%+0.98
15 Dec 20225.13%−0.49
30 Nov 20225.62%+0.19
15 Nov 20225.43%+0.60
31 Oct 20224.83%−0.10
14 Oct 20224.93%−0.18
30 Sep 20225.11%+0.32
15 Sep 20224.79%+0.40
31 Aug 20224.39%−0.37
15 Aug 20224.76%+0.46
29 Jul 20224.30%+0.02
15 Jul 20224.28%+0.24
30 Jun 20224.04%+0.06
15 Jun 20223.98%−0.24
31 May 20224.22%−0.81
13 May 20225.03%+0.42
29 Apr 20224.61%−0.66
14 Apr 20225.27%+0.19
31 Mar 20225.08%−0.09
15 Mar 20225.17%−0.21
28 Feb 20225.38%−1.24
15 Feb 20226.62%−0.12
31 Jan 20226.74%+1.63
14 Jan 20225.11%−0.08
31 Dec 20215.19%−0.04
15 Dec 20215.23%+0.39
30 Nov 20214.84%+0.46
15 Nov 20214.38%−0.51
29 Oct 20214.89%+0.09
15 Oct 20214.80%+0.09
30 Sep 20214.71%−0.37
15 Sep 20215.08%−0.37
31 Aug 20215.45%−0.50
13 Aug 20215.95%−0.56
30 Jul 20216.51%+0.43
15 Jul 20216.08%−0.31
30 Jun 20216.39%+0.03
15 Jun 20216.36%−1.34
28 May 20217.70%+0.08
14 May 20217.62%+0.31
30 Apr 20217.31%+0.40
15 Apr 20216.91%+0.64
31 Mar 20216.27%+0.13
15 Mar 20216.14%+0.06
26 Feb 20216.08%+0.40
12 Feb 20215.68%+0.28
29 Jan 20215.40%+0.14
15 Jan 20215.26%−0.30
31 Dec 20205.56%+0.39
15 Dec 20205.17%+0.11
30 Nov 20205.06%+0.20
13 Nov 20204.86%−0.29
30 Oct 20205.15%−0.69
15 Oct 20205.84%+0.01
30 Sep 20205.83%+0.17
15 Sep 20205.66%+0.22
31 Aug 20205.44%−0.04
14 Aug 20205.48%−0.35
31 Jul 20205.83%−0.30
15 Jul 20206.13%−0.07
30 Jun 20206.20%−0.38
15 Jun 20206.58%+0.26
29 May 20206.32%+0.27
15 May 20206.05%+0.26
30 Apr 20205.79%−0.22
15 Apr 20206.01%+0.03
31 Mar 20205.98%−0.28
13 Mar 20206.26%0.00
28 Feb 20206.26%+0.03
14 Feb 20206.23%−0.67
31 Jan 20206.90%+0.74
15 Jan 20206.16%+0.13
31 Dec 20196.03%+0.56
13 Dec 20195.47%−0.58
29 Nov 20196.05%−0.11
15 Nov 20196.16%−0.31
31 Oct 20196.47%−0.67
15 Oct 20197.14%–

Newest first. Scroll inside the table for earlier dates, back to 15 Oct 2019.

Frequently asked questions

How shorted is IONIS PHARMACEUTICALS INC right now?
12.57% of IONIS PHARMACEUTICALS INC's (IONS) shares outstanding were reported short for settlement date 15 Sep 2026, per FINRA's consolidated short interest report. That makes it the 446th most shorted US stock, out of 3,805 we rank.
What does this number include?
FINRA member firms must report their short positions in all US equities twice a month; FINRA consolidates them per security. We divide that official share count by the company's shares outstanding from its SEC filings. This is the regulatory figure, not a daily estimate.
Why does it only update twice a month?
US short interest is reported for settlement on the 15th and the last business day of each month, and FINRA publishes the consolidated figures about nine business days later. That cadence is set by regulation; no daily official figure exists.
Is this IONS's short float?
No. This is short interest as a percentage of shares outstanding, the count in the company's SEC filings. "Short float" divides the same FINRA short count by the public float, which excludes closely held shares, so it comes out higher for the same company. We publish no float estimates: the float is not a regulatory figure.
What is IONS's days to cover?
5.20 days for settlement date 15 Sep 2026: FINRA's own short interest ratio, the reported shares short divided by average daily trading volume. It is published in the same FINRA file and shown verbatim; we hold no volume data ourselves.
Which funds are short?
US public short interest is aggregate-only: individual short sellers are not named. Only some EU markets publish named positions.