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Income tax expense (Tables) | 12 Months Ended
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Dec. 31, 2021
Text block [abstract] |
Major Components of Income Tax Expense |
| (a) | Components of income tax expense:
|  | Year ended December 31, |
|  | 2019 |  |  | 2020 |  |  | 2021 |
|  | NT$000 |  |  | NT$000 |  |  | NT$000 |
Current income tax: |  |  |  |  |  |  |  |  |  |  |  |
Current income tax on profits for the period |  |  | 408,788 |  |  |  | 636,876 |  |  |  | 1,109,752 |
Income tax on unappropriated retained earnings |  |  | 74,540 |  |  |  | 105,665 |  |  |  | 227,467 |
Prior year income tax overestimation |  |  | (5,016 | ) |  |  | (133,923 | ) |  |  | (184,284 | )
Total current income tax |  |  | 478,312 |  |  |  | 608,618 |  |  |  | 1,152,935 |
Deferred income tax: |  |  |  |  |  |  |  |  |  |  |  |
Relating to origination and reversal of temporary differences |  |  | 35,367 |  |  |  | (14,237 | ) |  |  | (54,617 | )
Income tax expense |  |  | 513,679 |  |  |  | 594,381 |  |  |  | 1,098,318 |
Deferred Tax Charged to Other Comprehensive Income |
| (b) | The income tax (charge)/credit relating to components of other comprehensive income are as follows:
|  | Year ended December 31, |
|  | 2019 |  |  | 2020 |  |  | 2021 |
|  | NT$000 |  |  | NT$000 |  |  | NT$000 |
Unrealized (loss) gain on valuation of financial assets at fair value through other comprehensive income |  |  | (7,016 | ) |  |  | 34,794 |  |  |  | 30,459 |
Remeasurement of defined benefit obligations |  |  | 4,183 |  |  |  | (10,398 | ) |  |  | (2,999 | )
|  |  | (2,833 | ) |  |  | 24,396 |  |  |  | 27,460 |
Reconciliation of Income Tax Expense and Accounting Profit Before Income Tax |
| b) | Reconciliation of income tax expense and the accounting profit:
|  | Year ended December 31, |
|  | 2019 |  |  | 2020 |  |  | 2021 |
|  | NT$000 |  |  | NT$000 |  |  | NT$000 |
Tax calculated based on profit before tax and statutory tax rate |  |  | 606,917 |  |  |  | 595,258 |  |  |  | 1,207,605 |
Effects from adjustments based on regulation |  |  | (162,924 | ) |  |  | 26,974 |  |  |  | (152,618 | )
Temporary difference not recognized as deferred tax assets |  |  | (608 | ) |  |  | (4 | ) |  |  | — |
Prior year income tax overestimation |  |  | (5,016 | ) |  |  | (133,923 | ) |  |  | (184,284 | )
Income tax on unappropriated retained earnings |  |  | 74,540 |  |  |  | 105,665 |  |  |  | 227,467 |
Effect of different tax rates in countries in which the Group operates |  |  | 770 |  |  |  | 411 |  |  |  | 148 |
Income tax expense |  |  | 513,679 |  |  |  | 594,381 |  |  |  | 1,098,318 |
Details of Deferred Tax Assets (Liabilities) |
| c) | The amounts of deferred tax assets or liabilities resulting from temporary differences and investment tax credits are as follows:
|  | 2019 |
|  | January 1 |  |  | Recognized in profit or loss |  |  | Recognized in other comprehensive income |  |  | December 31 |
|  | NT$000 |  |  | NT$000 |  |  | NT$000 |  |  | NT$000 |
Deferred tax assets |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss on inventories |  |  | 7,232 |  |  |  | 5,468 |  |  |  | — |  |  |  | 12,700 |
Property, plant and equipment |  |  | 64,183 |  |  |  | (25,515 | ) |  |  | — |  |  |  | 38,668 |
Provisions |  |  | 12,396 |  |  |  | (6,796 | ) |  |  | — |  |  |  | 5,600 |
Deferred revenue |  |  | 34,156 |  |  |  | (6,506 | ) |  |  | — |  |  |  | 27,650 |
Net defined benefit liability |  |  | 100,743 |  |  |  | (3,948 | ) |  |  | (4,183 | ) |  |  | 92,612 |
Unrealized exchange losses |  |  | 3,575 |  |  |  | 13,721 |  |  |  | — |  |  |  | 17,296 |
Investment tax credit |  |  | 4,420 |  |  |  | (4,420 | ) |  |  | — |  |  |  | — |
Others |  |  | 11 |  |  |  | 15 |  |  |  | — |  |  |  | 26 |
Total |  |  | 226,716 |  |  |  | (27,981 | ) |  |  | (4,183 | ) |  |  | 194,552 |
Deferred tax liabilities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Property, plant and equipment |  |  | (281,594 | ) |  |  | (7,386 | ) |  |  | — |  |  |  | (288,980 | )
Financial assets at fair value through other comprehensive income |  |  | (27,165 | ) |  |  | — |  |  |  | 7,016 |  |  |  | (20,149 | )
Total |  |  | (308,759 | ) |  |  | (7,386 | ) |  |  | 7,016 |  |  |  | (309,129 | )
Information presented on statements of financial position |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred tax assets |  |  | 226,716 |  |  |  |  |  |  |  |  |  |  |  | 194,552 |
Deferred tax liabilities |  |  | (308,759 | ) |  |  |  |  |  |  |  |  |  |  | (309,129 | )
|  | 2020 |
|  | January 1 |  |  | Recognized in profit or loss |  |  | Recognized in other comprehensive income |  |  | December 31 |
|  | NT$000 |  |  | NT$000 |  |  | NT$000 |  |  | NT$000 |
Deferred tax assets |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss on inventories |  |  | 12,700 |  |  |  | 3,263 |  |  |  | — |  |  |  | 15,963 |
Property, plant and equipment |  |  | 38,668 |  |  |  | (2,267 | ) |  |  | — |  |  |  | 36,401 |
Provisions |  |  | 5,600 |  |  |  | (2,922 | ) |  |  | — |  |  |  | 2,678 |
Deferred revenue |  |  | 27,650 |  |  |  | (6,506 | ) |  |  | — |  |  |  | 21,144 |
Net defined benefit liability |  |  | 92,612 |  |  |  | (4,089 | ) |  |  | 10,398 |  |  |  | 98,921 |
Unrealized exchange losses |  |  | 17,296 |  |  |  | (7,381 | ) |  |  | — |  |  |  | 9,915 |
Others |  |  | 26 |  |  |  | 643 |  |  |  | — |  |  |  | 669 |
Total |  |  | 194,552 |  |  |  | (19,259 | ) |  |  | 10,398 |  |  |  | 185,691 |
Deferred tax liabilities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Property, plant and equipment |  |  | (288,980 | ) |  |  | 33,496 |  |  |  | — |  |  |  | (255,484 | )
Financial assets at fair value through other comprehensive income |  |  | (20,149 | ) |  |  | — |  |  |  | (34,794 | ) |  |  | (54,943 | )
Total |  |  | (309,129 | ) |  |  | 33,496 |  |  |  | (34,794 | ) |  |  | (310,427 | )
Information presented on statements of financial position |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred tax assets |  |  | 194,552 |  |  |  |  |  |  |  |  |  |  |  | 185,691 |
Deferred tax liabilities |  |  | (309,129 | ) |  |  |  |  |  |  |  |  |  |  | (310,427 | )
|  | 2021 |
|  | January 1 |  |  | Recognized in profit or loss |  |  | Recognized in other comprehensive income |  |  | December 31 |
|  | NT$000 |  |  | NT$000 |  |  | NT$000 |  |  | NT$000 |
Deferred tax assets |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss on inventories |  |  | 15,963 |  |  |  | 8,354 |  |  |  | — |  |  |  | 24,317 |
Property, plant and equipment |  |  | 36,401 |  |  |  | 235 |  |  |  | — |  |  |  | 36,636 |
Provisions |  |  | 2,678 |  |  |  | 171 |  |  |  | — |  |  |  | 2,849 |
Deferred revenue |  |  | 21,144 |  |  |  | (6,506 | ) |  |  | — |  |  |  | 14,638 |
Net defined benefit liability |  |  | 98,921 |  |  |  | (4,672 | ) |  |  | 2,999 |  |  |  | 97,248 |
Unrealized exchange losses |  |  | 9,915 |  |  |  | (7,754 | ) |  |  | — |  |  |  | 2,161 |
Others |  |  | 669 |  |  |  | 2,080 |  |  |  | — |  |  |  | 2,749 |
Total |  |  | 185,691 |  |  |  | (8,092 | ) |  |  | 2,999 |  |  |  | 180,598 |
Deferred tax liabilities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Property, plant and equipment |  |  | (255,484 | ) |  |  | 62,797 |  |  |  | — |  |  |  | (192,687 | )
Financial assets at fair value through other comprehensive income |  |  | (54,943 | ) |  |  | — |  |  |  | (30,459 | ) |  |  | (85,402 | )
Others |  |  | — |  |  |  | (88 | ) |  |  | — |  |  |  | (88 | )
Total |  |  | (310,427 | ) |  |  | 62,709 |  |  |  | (30,459 | ) |  |  | (278,177 | )
Information presented on statements of financial position |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred tax assets |  |  | 185,691 |  |  |  |  |  |  |  |  |  |  |  | 180,598 |
Deferred tax liabilities |  |  | (310,427 | ) |  |  |  |  |  |  |  |  |  |  | (278,177 | )
Summary of Deductible Temporary Differences for which No Deferred Tax Asset Is Recognized |
| d) | The amounts of deductible temporary difference that are not recognized as deferred tax assets are as follows:
|  | December 31, 2020 |  |  | December 31, 2021 |
|  | NT$000 |  |  | NT$000 |
Deductible temporary differences |  |  | 946,236 |  |  |  | 371,133 |

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