United Microelectronics (UMC)

United Microelectronics on one page: short interest, daily short volume, fails to deliver, large holders, 13F holders and insider trades. Listed on NYSE, classified by the SEC as semiconductors & related devices.

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27.8M

Short interest

settlement 2026-09-30

2.4

Days to cover

-1.2 days vs prior

61.8%

Short share of volume

2026-10-09

1,493

Fails to deliver

settlement 2026-09-14

-$230.4M

Insider flow, 90 days

0 buys, 3 sells

As of 2026-10-09.

Short interest

FINRA, twice a month. The newest 24 settlements in the table, 48 in the chart. JSON

As of 30 September 2026, short interest in UMC is 27,794,121 shares, down 5,874,050 shares over the last month. Over the last 48 readings it ranged from 20,511,587 shares (15 July 2026) to 87,209,066 shares (14 March 2025). At the reported average volume of 11.6M shares a day that is 2.4 days to cover.

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Settlement	Shares short	Change	Avg daily volume	Days to cover
2026-09-30	27,794,121	-27.6%	11,615,278	2.39
2026-09-15	38,400,261	+14.1%	10,796,618	3.56
2026-08-31	33,668,171	+13.4%	11,387,541	2.96
2026-08-14	29,695,086	-13.2%	11,518,388	2.58
2026-07-31	34,193,634	+66.7%	17,966,337	1.90
2026-07-15	20,511,587	-21.6%	16,495,511	1.24
2026-06-30	26,177,159	+3.3%	20,022,281	1.31
2026-06-15	25,331,010	-2.9%	18,766,216	1.35
2026-05-29	26,098,399	-3.0%	17,881,650	1.46
2026-05-15	26,916,938	+0.9%	16,420,260	1.64
2026-04-30	26,664,075	+3.2%	15,089,895	1.77
2026-04-15	25,829,756	-14.7%	8,405,258	3.07
2026-03-31	30,266,600	-11.5%	8,189,437	3.70
2026-03-13	34,188,481	+12.3%	8,586,222	3.98
2026-02-27	30,437,470	-3.7%	6,529,546	4.66
2026-02-13	31,611,829	-0.8%	10,580,372	2.99
2026-01-30	31,857,208	-33.6%	18,377,538	1.73
2026-01-15	48,007,369	+14.1%	11,791,503	4.07
2025-12-31	42,091,913	-8.3%	6,468,290	6.51
2025-12-15	45,911,313	-4.1%	9,342,293	4.91
2025-11-28	47,854,483	-5.4%	8,284,842	5.78
2025-11-14	50,568,495	-2.8%	8,339,152	6.06
2025-10-31	52,022,809	+8.3%	7,565,953	6.88
2025-10-15	48,044,444	-12.2%	8,446,717	5.69

Daily short volume

FINRA Reg SHO, the last 30 sessions. JSON

As of 9 October 2026, the short share of UMC volume is 61.8%, down 2.0 points over the last five sessions. Over the last 30 readings it ranged from 37.4% (6 October 2026) to 78.9% (8 September 2026). The latest reading is in line with the 30-session average of 62.4%, on 1.4M shares reported.

Date	Short volume	Total volume	Short share	Exempt
2026-10-09	853K	1.4M	61.8%	2,316
2026-10-08	2.0M	3.2M	60.8%	18
2026-10-07	1.4M	2.6M	53.0%	571
2026-10-06	2.4M	6.3M	37.4%	198,762
2026-10-05	6.9M	10.5M	65.4%	251,828
2026-10-02	1.8M	2.9M	63.7%	32
2026-10-01	1.1M	1.9M	60.5%	2,757
2026-09-30	1.0M	1.8M	57.5%	1,133
2026-09-29	1.8M	2.8M	65.8%	3,676
2026-09-28	752K	1.4M	53.6%	2
2026-09-25	1.0M	1.5M	65.3%	0
2026-09-24	967K	2.0M	48.7%	515
2026-09-23	2.1M	3.4M	60.0%	51
2026-09-22	1.4M	2.2M	63.1%	0
2026-09-21	1.6M	2.6M	62.2%	112
2026-09-18	1.9M	3.0M	63.4%	31
2026-09-17	3.3M	5.2M	63.1%	224
2026-09-16	1.5M	2.7M	56.4%	5,259
2026-09-15	1.3M	2.6M	49.3%	837
2026-09-14	1.7M	2.5M	67.8%	100
2026-09-11	1.1M	1.6M	71.3%	653
2026-09-10	1.3M	2.2M	61.0%	4,806
2026-09-09	1.9M	2.7M	71.0%	2,270
2026-09-08	3.0M	3.8M	78.9%	5,240
2026-09-04	1.5M	2.1M	71.2%	31
2026-09-03	1.1M	1.6M	67.6%	3,300
2026-09-02	1.3M	2.1M	63.7%	445
2026-09-01	3.8M	4.9M	76.3%	295
2026-08-31	1.5M	2.4M	62.3%	10,728
2026-08-28	3.2M	4.5M	71.2%	3,736

Fails to deliver

SEC, the last 30 settlement dates with a fail. JSON

As of 14 September 2026, the fails-to-deliver balance in UMC is 1,493 shares, down 18,405 shares over the last settlement date. Over the last 30 readings it ranged from 13 shares (5 August 2026) to 585,183 shares (3 September 2026). The latest reading sits at the bottom of that range.

Settlement	Shares failed	Price	Value
2026-09-14	1,493	$22.64	$34K
2026-09-11	19,898	$22.12	$440K
2026-09-10	14,746	$22.69	$335K
2026-09-09	201,383	$21.82	$4.4M
2026-09-08	78,852	$20.77	$1.6M
2026-09-04	6,674	$19.86	$133K
2026-09-03	585,183	$19.97	$11.7M
2026-09-02	11,761	$20.47	$241K
2026-09-01	183,800	$19.88	$3.7M
2026-08-31	97,168	$19.79	$1.9M
2026-08-28	40,777	$19.07	$778K
2026-08-26	1,130	$19.60	$22K
2026-08-25	1,345	$19.05	$26K
2026-08-24	404	$18.34	$7K
2026-08-21	267,340	$18.00	$4.8M
2026-08-18	287	$19.53	$6K
2026-08-10	55,000	$18.72	$1.0M
2026-08-07	71,052	$19.20	$1.4M
2026-08-06	263,570	$19.29	$5.1M
2026-08-05	13	$20.63	$268
2026-08-04	26,473	$18.69	$495K
2026-08-03	77	$19.03	$1K
2026-07-31	19,357	$18.94	$367K
2026-07-29	14,220	$17.36	$247K
2026-07-27	236	$19.48	$5K
2026-07-24	118,117	$20.87	$2.5M
2026-07-23	122,751	$21.29	$2.6M
2026-07-17	910	$22.29	$20K
2026-07-16	549	$24.92	$14K
2026-07-15	399	$23.84	$10K

Insider trades

SEC Form 4, newest first. JSON

Insiders at UMC reported 3 open-market sells worth $230.4M in the last 90 days and no open-market buys. Latest filing: LIN JEN-TSUNG (Vice President) on 2026-09-22.

Date	Insider	Title	Type	Shares	Price	Value	Owned after
2026-09-22	LIN JEN-TSUNG	Vice President	Sell	10K	$163.00	$1.6M	1.2M
2026-09-17	Liu Chitung	CFO & SVP	Sell	400K	$145.00	$58.0M	2.6M
2026-09-16	Liu Chitung	CFO & SVP	Sell	1.2M	$142.33	$170.8M	3.0M
2026-09-07	Liu Chitung	CFO & SVP	J	1.0M	$0.00	$0	1.0M
2026-09-07	Liu Chitung	CFO & SVP	J	1.0M	$0.00	$0	4.3M
2026-07-13	Liu Chitung	CFO & SVP	Sell	1.9M	$154.89	$294.3M	3.3M
2026-06-30	HU CHE-JEN	Vice President	Sell	10K	$171.30	$1.7M	3.2M

Form 4 filings are due within two business days of the trade. Insiders sell for many reasons that say nothing about the company; open-market buys are rarer.

Large holders (13D and 13G)

One row per reporting person with its latest filing, newest first. JSON

1 holder reports 5% or more of UMC in its latest filing, on Schedule 13G (passive). The holder is BlackRock, Inc. at 6.5% of the class (817,485,069 shares), filed 2026-04-29 for an event on 2026-03-31.

Filed	Form	Holder	Shares	Of class	Event
2026-04-29	13G/Ano. 3	BlackRock, Inc.parent holding company	817.5M	6.5%	2026-03-31

13F holders

Tracked managers holding UMC at their latest 13F. JSON

5 of the 30 tracked managers held UMC at their latest 13F, $318.9M in total at quarter-end prices. AQR Capital Management is the largest at $210.0M (0.1% of its portfolio) as of 2026-06-30. Over the prior quarter 0 added shares and 5 cut.

Fund	Quarter	Shares	Value	Of portfolio	Change in shares
AQR Capital Management	2026-06-30	7.7M	$210.0M	0.07%	-7.0M
Two Sigma Investments	2026-06-30	3.1M	$84.0M	0.06%	-6.6M
Millennium Management	2026-06-30	506K	$13.8M	0.01%	-1.3M
Citadel Advisors	2026-06-30	210K	$5.7M	0.00%	-555K
D. E. Shaw & Co.	2026-06-30	196K	$5.3M	0.00%	-1.7M

Only the 30 tracked managers on the funds hub; a 13F reports long positions in US listed stock at quarter end, 45 days late, and says nothing about shorts or positions sold since.

What this page is

United Microelectronics in the regulatory record

Regulators publish company data in separate files that never sit next to each other: FINRA's twice-monthly short interest, its daily short sale volume, the SEC's fails-to-deliver counts, and each insider's Form 4. A company page puts those series for one ticker on one URL, with planned sales, large holders, 13F holders and financials beside them, so the short position, the daily flow, the settlement fails and what insiders are doing can be read together.

Each section has its own history table, a one-line summary of the latest figures and its own JSON and CSV links, and says when its source last updated.

This page follows United Microelectronics (UMC), SEC CIK 1033767, listed on NYSE, classified by the SEC as semiconductors & related devices. The cross-market tables live on the short interest and insider transactions hubs.

Source and updates

Short interest: FINRA consolidated short interestSource: FINRA.Twice a month, about eight business days after settlement. Latest 2026-09-30.JSON and CSV
Daily short volume: FINRA Reg SHO daily filesSource: FINRA.Every trading day, the morning after FINRA posts it. Latest 2026-10-09.JSON and CSV
Fails to deliver: SEC fails-to-deliver dataSource: SEC.Twice a month, a few weeks after the half month ends. Latest 2026-09-14.JSON and CSV
Large holders: SEC EDGAR Schedule 13D and 13GSource: SEC.New filings appear shortly after the SEC posts them. A 13D is due within five business days of crossing 5%; a 13G follows the passive schedule. Latest 2026-04-29.JSON and CSV
13F holders: SEC EDGAR Form 13F-HRSource: SEC.Quarterly, filed within 45 days of quarter end; 30 tracked managers. Latest 2026-06-30.JSON and CSV
Insider trades: SEC EDGAR Form 4Source: SEC.New filings appear shortly after the SEC posts them; they're due two business days after the trade. Latest 2026-09-22.JSON and CSV
Company record: EDGAR filing index for CIK 1033767Ticker, name and exchange from the SEC's company list, refreshed weekly.
Rate limits: 10 requests a minute without a key, 30 with a free key from a free account.

How to read it

Read the position against the flow: rising short interest with a high daily short share is new shorting; rising short interest with a normal short share is old shorts holding on.
Insider buys next to a large short position are rare and stand out; insider sells next to one are common and mean little.
Fails to deliver matter relative to the float, not in absolute shares; a million failed shares in a mega cap is noise.

Analysis of what the data shows, not advice. XOOMAR does not recommend buying, selling or holding anything.

Datasets

Frequently Asked Questions

How much of UMC is sold short?

27,794,121 shares were held short at the 2026-09-30 settlement, 2.4 days of average volume. FINRA publishes the next count about eight business days after the 15th and the last business day of the month.

What is UMC's daily short volume?

On 2026-10-09, 853,202 of the 1,381,692 UMC shares reported to FINRA were sold short, 61.8% of the day's reported volume. Short volume is a flow for one day, not a position.

Does UMC have fails to deliver?

The SEC's latest file shows 1,493 UMC shares failed to deliver at settlement 2026-09-14. Fails are reported per settlement date and published twice a month with a lag.

Are UMC insiders buying or selling?

Insiders at UMC reported 3 open-market sells worth $230.4M in the last 90 days and no open-market buys. Latest filing: LIN JEN-TSUNG (Vice President) on 2026-09-22.

Who owns 5% or more of UMC?

Which tracked 13F managers own UMC?

5 of the 30 tracked 13F managers held UMC shares at their latest filing, $318.9M in all. The largest: Cliff Asness's AQR Capital Management (7.7M shares, $210.0M), Two Sigma Investments (3.1M shares, $84.0M), Izzy Englander's Millennium Management (506K shares, $13.8M), Ken Griffin's Citadel Advisors (210K shares, $5.7M), D. E. Shaw & Co. (196K shares, $5.3M).

Data on this page is provided for informational purposes only and is not financial advice. See our editorial policy.

United Microelectronics (UMC)

Short interest

Daily short volume

Fails to deliver

Insider trades

Large holders (13D and 13G)

13F holders

United Microelectronics in the regulatory record

Source and updates

How to read it

Other companies the SEC classifies as semiconductors & related devices

Datasets

Frequently Asked Questions