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Contents of Significant Accounts - Reconciliation Between Income Tax Expense and Income Before Tax At UMC's Applicable Tax Rate (Detail) $ in Thousands, $ in Thousands | 12 Months Ended
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Dec. 31, 2024 TWD ($) | Dec. 31, 2024 USD ($) | Dec. 31, 2023 TWD ($) | Dec. 31, 2022 TWD ($)
Reconciliation of accounting profit multiplied by applicable tax rates [abstract] |  |  |  |
Income before tax | $ 57,044,820 | $ 1,739,702 | $ 68,450,404 | $ 109,625,660
At UMC's statutory income tax rate | 11,408,964 |  | 13,690,081 | 21,925,132
Adjustments in respect of current income tax of prior periods | (124,430) |  | (217,891) | (585,941)
Net changes in loss carry-forward and investment tax credits | (2,026,085) |  | (2,179,234) | (465,152)
Adjustment of deferred tax assets/liabilities for write-downs/reversals and different jurisdictional tax rates | 559,386 |  | 211,639 | (281,319)
Tax effect of non-taxable income and non-deductible expenses: |  |  |  |
Tax exempt income | (472,756) |  | (1,428,035) | (4,384,566)
Investment loss (gain) | 205,207 |  | (755,800) | 1,827,822
Dividend income | (231,267) |  | (323,182) | (423,027)
Others | (610,092) |  | (145,520) | (340,745)
Basic tax | 13,414 |  | 43,506 | 0
Estimated income tax on unappropriated earnings | (743,264) |  | (1,160,324) | 1,247,910
Deferred income tax related to changes in tax rates | 68 |  | 0 | 0
Effect of different tax rates applicable to UMC and its subsidiaries | 15,673 |  | 234,510 | 605,929
Taxes withheld in other jurisdictions | 44,489 |  | 38,346 | 35,979
Others | 330,887 |  | 303,174 | 164,873
Income tax expense recorded in profit or loss | $ 8,370,194 | $ 255,267 | $ 8,311,270 | $ 19,326,895

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- Definition The aggregate amount included in the determination of profit (loss) for the period in respect of current tax and deferred tax. [Refer: Current tax expense (income); Deferred tax expense (income)] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 8 -IssueDate 2024-01-01 -Paragraph 23 -Subparagraph h -URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=8&code=ifrs-tx-2024-en-r&anchor=para_23_h&doctype=Standard -URIDate 2024-03-27 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 26 -IssueDate 2024-01-01 -Paragraph 35 -Subparagraph b -Clause viii -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=26&code=ifrs-tx-2024-en-r&anchor=para_35_b_viii&doctype=Standard -URIDate 2024-03-27 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2024-01-01 -Paragraph 79 -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2024-en-r&anchor=para_79&doctype=Standard -URIDate 2024-03-27 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2024-01-01 -Paragraph 81 -Subparagraph c -Clause i -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2024-en-r&anchor=para_81_c_i&doctype=Standard -URIDate 2024-03-27 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2024-01-01 -Paragraph 81 -Subparagraph c -Clause ii -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2024-en-r&anchor=para_81_c_ii&doctype=Standard -URIDate 2024-03-27 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 12 -IssueDate 2024-01-01 -Paragraph B13 -Subparagraph g -URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2024-en-r&anchor=para_B13_g&doctype=Appendix&subtype=B -URIDate 2024-03-27 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2024-01-01 -Paragraph 82 -Subparagraph d -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2024-en-r&anchor=para_82_d&doctype=Standard -URIDate 2024-03-27 + Details
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- Definition The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that relates to foreign tax rates. [Refer: Accounting profit] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 12 -IssueDate 2024-01-01 -Paragraph 81 -Subparagraph c -Clause i -URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=12&code=ifrs-tx-2024-en-r&anchor=para_81_c_i&doctype=Standard -URIDate 2024-03-27 + Details
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