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Financial Risk and Fair Value Disclosures (Tables)

12 Months Ended

Dec. 31, 2024

Disclosure of detailed information about financial instruments [line items]

Categories of Financial Instruments

(1) Categories of financial instruments

		As of December 31,
Financial Assets		2023				2024
		NT$				NT$
		(In Thousands)				(In Thousands)
Financial assets at fair value through profit or loss		$	17,138,461			$	18,456,932
Financial assets at fair value through other comprehensive income			17,683,960				17,209,328
Financial assets measured at amortized cost
Cash and cash equivalents (cash on hand excluded)			132,547,415				104,993,968
Receivables			32,292,914				34,994,933
Refundable deposits			2,708,823				1,992,400
Other financial assets			6,353,768				3,739,224
Total		$	208,725,341			$	181,386,785

		As of December 31,
Financial Liabilities		2023				2024
		NT$				NT$
		(In Thousands)				(In Thousands)
Financial liabilities at fair value through profit or loss		$	1,019,362			$	901,000
Financial liabilities measured at amortized cost
Short-term loans			13,530,000				8,515,000
Payables			52,393,399				42,259,798
Guarantee deposits (current portion included)			41,599,386				42,874,494
Bonds payable (current portion included)			38,359,352				30,051,568
Long-term loans (current portion included)			22,883,344				36,476,909
Lease liabilities			5,393,187				6,419,016
Total		$	175,178,030			$	167,497,785

Maturity Profile of Financial Liabilities Based on Contractual Undiscounted Payments and Contractual Maturity

The table below summarizes the maturity profile of the Company’s financial liabilities based on the contractual undiscounted payments and contractual maturity:

		As of December 31, 2023
		Less than 1 year				2 to 3 years				4 to 5 years				> 5 years				Total
		NT$				NT$				NT$				NT$				NT$
		(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)
Non-derivative financial liabilities
Short-term loans		$	13,780,612			$	—			$	—			$	—			$	13,780,612
Payables			52,202,821				—				—				—				52,202,821
Guarantee deposits			1,476,430				3,556,179				25,955,654				10,611,123				41,599,386
Bonds payable (Note A)			14,797,772				10,980,506				12,321,345				2,132,963				40,232,586
Long-term loans			2,872,168				14,406,101				5,071,743				2,940,524				25,290,536
Lease liabilities			649,879				1,311,239				1,223,724				3,712,729				6,897,571
Total		$	85,779,682			$	30,254,025			$	44,572,466			$	19,397,339			$	180,003,512
		As of December 31, 2024
		Less than 1 year				2 to 3 years				4 to 5 years				> 5 years				Total
		NT$				NT$				NT$				NT$				NT$
		(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)
Non-derivative financial liabilities
Short-term loans		$	8,683,215			$	—			$	—			$	—			$	8,683,215
Payables			42,136,632				—				—				—				42,136,632
Guarantee deposits			921,134				4,571,633				27,522,150				9,859,577				42,874,494
Bonds payable (Note A)			340,976				16,675,030				12,146,745				2,118,683				31,281,434
Long-term loans (Note B)			6,354,561				11,490,087				21,478,391				93,106				39,416,145
Lease liabilities			830,618				1,509,438				1,437,870				4,442,706				8,220,632
Total		$	59,267,136			$	34,246,188			$	62,585,156			$	16,514,072			$	172,612,552
Derivative financial liabilities
Forward exchange contracts
Net settlement-outflow		$	(1,039	)		$	—			$	—			$	—			$	(1,039	)

Details of Forward Exchange Contracts

The details of forward exchange contracts entered into by UMC are summarized as follows:

As of December 31, 2023

Forward exchange contracts have been settled.

As of December 31, 2024

Type		Notional Amount		Contract Period
Forward exchange contracts		Sell USD 24 million		December 27, 2024 - January 21, 2025

Reconciliation for Fair Value Measurement in Level 3 Fair Value Hierarchy

Reconciliation for fair value measurement in Level 3 fair value hierarchy were as follows:

		Financial assets at fair value through profit or loss																								Financial assets at fair value through other comprehensive income
		Common stock				Preferred stock				Funds				Convertible bonds				Others				Total				Common stock				Preferred stock				Total
		NT$				NT$				NT$				NT$				NT$				NT$				NT$				NT$				NT$
		(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)
As of January 1, 2023		$	3,198,808			$	2,865,258			$	4,626,333			$	36,474			$	—			$	10,726,873			$	3,427,720			$	182,547			$	3,610,267
Recognized in profit (loss)			(312,149	)			(277,994	)			(617,764	)			(8,828	)			—				(1,216,735	)			—				—				—
Recognized in other comprehensive income (loss)			—				—				—				—				—				—				(365,395	)			(7,484	)			(372,879	)
Acquisition			610,153				294,046				294,245				—				154,761				1,353,205				—				—				—
Disposal			—				(89,997	)			—				(27,740	)			—				(117,737	)			—				—				—
Return of capital			(1,384	)			—				(36,346	)			—				—				(37,730	)			—				—				—
Transfer out of Level 3			(461,403	)			—				—				—				—				(461,403	)			—				—				—
Exchange effect			2,230				(4,679	)			8,428				94				(1,461	)			4,612				—				—				—
As of December 31, 2023		$	3,036,255			$	2,786,634			$	4,274,896			$	—			$	153,300			$	10,251,085			$	3,062,325			$	175,063			$	3,237,388

		Financial assets at fair value through profit or loss																								Financial assets at fair value through other comprehensive income
		Common stock				Preferred stock				Funds				Convertible bonds				Others				Total				Common stock				Preferred stock				Total
		NT$				NT$				NT$				NT$				NT$				NT$				NT$				NT$				NT$
		(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)
As of January 1, 2024		$	3,036,255			$	2,786,634			$	4,274,896			$	—			$	153,300			$	10,251,085			$	3,062,325			$	175,063			$	3,237,388
Recognized in profit (loss)			(119,584	)			187,131				128,617				3,120				4,140				203,424				—				—				—
Recognized in other comprehensive income (loss)			—				—				—				—				—				—				104,499				29,817				134,316
Acquisition			505,538				639,779				1,133,312				51,191				—				2,329,820				64,694				—				64,694
Disposal			(78,234	)			(311,066	)			(81,371	)			—				(96,312	)			(566,983	)			—				—				—
Return of capital			(83	)			—				(12,405	)			—				—				(12,488	)			—				—				—
Transfer out of Level 3			(377,121	)			—				—				—				—				(377,121	)			—				—				—
Exchange effect			41,412				101,455				153,398				455				4,332				301,052				—				—				—
As of December 31, 2024		$	3,008,183			$	3,403,933			$	5,596,447			$	54,766			$	65,460			$	12,128,789			$	3,231,518			$	204,880			$	3,436,398

Reconciliation for Fair Value Measurement in Level 3 Derivatives Financial Liabilities

		Financial liabilities at fair value through profit or loss
		Derivatives
		NT$ (In Thousands)
As of January 1, 2023		$	438,397
Recognized in loss (profit)			580,965
As of December 31, 2023		$	1,019,362

		Financial liabilities at fair value through profit or loss
		Derivatives
		NT$ (In Thousands)
As of January 1, 2024		$	1,019,362
Recognized in loss (profit)			(119,401	)
As of December 31, 2024		$	899,961

Summary of Significant Unobservable Inputs of Fair Value Measurement in Level 3 Fair Value Hierarchy

Significant unobservable inputs of fair value measurement in Level 3 fair value hierarchy were as follows:

As of December 31, 2023
Category		Valuation technique		Significant unobservable inputs		Quantitative information		Interrelationship between inputs and fair value		Sensitivity analysis of interrelationship between inputs and fair value
Unlisted stock		Market approach		Discount for lack of marketability		0% - 50%		The greater degree of lack of marketability, the lower the estimated fair value is determined.		A change of 5% in the discount for lack of marketability of the aforementioned fair values of unlisted stocks could decrease/increase the Company’s profit (loss) for the year ended December 31, 2023 by NT$261 million and NT$199 million, respectively, and decrease/increase the Company’s other comprehensive income (loss) for the year ended December 31, 2023 by NT$214 million.
Fund		Net asset value approach		N/A		N/A		N/A		N/A
Embedded derivatives in exchangeable bonds		Binomial tree valuation model		Volatility		27.70%		The higher the volatility, the higher the estimated fair value is determined.		A change of 5% in the volatility could decrease/increase the Company’s profit (loss) for the year ended December 31, 2023 by NT$119 million and NT$131 million, respectively.

As of December 31, 2024
Category		Valuation technique		Significant unobservable inputs		Quantitative information		Interrelationship between inputs and fair value		Sensitivity analysis of interrelationship between inputs and fair value
Unlisted stock		Market approach		Discount for lack of marketability		0% - 50%		The greater degree of lack of marketability, the lower the estimated fair value is determined.		A change of 5% in the discount for lack of marketability of the aforementioned fair values of unlisted stocks could decrease/increase the Company’s profit (loss) for the year ended December 31, 2024 by NT$309 million and NT$244 million, respectively, and decrease/increase the Company’s other comprehensive income (loss) for the year ended December 31, 2024 by NT$239 million.
Fund		Net asset value approach		N/A		N/A		N/A		N/A
Convertible bonds		Binomial tree valuation model		Volatility		54.85%		The higher the volatility, the higher the estimated fair value is determined.		A change of 5% in the volatility could increase/decrease the Company’s profit (loss) for the year ended December 31, 2024 by NT$0.3 million and NT$0.4 million, respectively.
Embedded derivatives in exchangeable bonds		Binomial tree valuation model		Volatility		28.06%		The higher the volatility, the higher the estimated fair value is determined.		A change of 5% in the volatility could decrease/increase the Company’s profit (loss) for the year ended December 31, 2024 by NT$97 million and NT$113 million, respectively.

Recurring fair value measurement [member]

Disclosure of detailed information about financial instruments [line items]

Assets and Liabilities Measured and Recorded at Fair Value

a. Assets and liabilities measured and recorded at fair value on a recurring basis:

		As of December 31, 2023
		Level 1				Level 2				Level 3				Total
		NT$				NT$				NT$				NT$
		(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)
Financial assets:
Financial assets at fair value through profit or loss, current		$	443,601			$	—			$	—			$	443,601
Financial assets at fair value through profit or loss, noncurrent			6,424,475				19,300				10,251,085				16,694,860
Financial assets at fair value through other comprehensive income, current			5,753,379				—				—				5,753,379
Financial assets at fair value through other comprehensive income, noncurrent			8,693,193				—				3,237,388				11,930,581
Financial liabilities:
Financial liabilities at fair value through profit or loss, current			—				—				1,019,362				1,019,362

		As of December 31, 2024
		Level 1				Level 2				Level 3				Total
		NT$				NT$				NT$				NT$
		(In Thousands)				(In Thousands)				(In Thousands)				(In Thousands)
Financial assets:
Financial assets at fair value through profit or loss, current		$	606,016			$	2			$	—			$	606,018
Financial assets at fair value through profit or loss, noncurrent			5,703,325				18,800				12,128,789				17,850,914
Financial assets at fair value through other comprehensive income, current			5,893,377				—				—				5,893,377
Financial assets at fair value through other comprehensive income, noncurrent			7,879,553				—				3,436,398				11,315,951
Financial liabilities:
Financial liabilities at fair value through profit or loss, current			—				1,039				899,961				901,000

Not measured at fair value in statement of financial position but for which fair value is disclosed [member]

Disclosure of detailed information about financial instruments [line items]

Assets and Liabilities Measured and Recorded at Fair Value

As of December 31, 2023
						Fair value measurements during reporting period using
Items		Fair value				Level 1				Level 2				Level 3				Carrying amount
		NT$ (In Thousands)				NT$ (In Thousands)				NT$ (In Thousands)				NT$ (In Thousands)				NT$ (In Thousands)
Bonds payables (current portion included)		$	38,367,168			$	32,827,211			$	5,539,957			$	—			$	38,359,352
Long-term loans (current portion included)			22,883,344				—				22,883,344				—				22,883,344

As of December 31, 2024
						Fair value measurements during reporting period using
Items		Fair value				Level 1				Level 2				Level 3				Carrying amount
		NT$ (In Thousands)				NT$ (In Thousands)				NT$ (In Thousands)				NT$ (In Thousands)				NT$ (In Thousands)
Bonds payables (current portion included)		$	30,020,005			$	24,409,952			$	5,610,053			$	—			$	30,051,568
Long-term loans (current portion included)			36,476,909				—				36,476,909				—				36,476,909

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