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Income Tax - Major Components of Income Tax Expense (Detail) $ in Millions, $ in Millions | 12 Months Ended
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Dec. 31, 2020 TWD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 TWD ($) | Dec. 31, 2018 TWD ($)
Current tax |  |  |  |
Current tax expenses recognized for the year | $ 8,172 |  | $ 8,109 | $ 8,271
Income tax on unappropriated earnings | 8 |  | (20) | (2,070)
Income tax adjustments on prior years | (22) |  | (91) | 7
Others | 19 |  | 12 | 8
Current tax | 8,177 |  | 8,010 | 6,216
Deferred tax |  |  |  |
Deferred tax expense (benefits) recognized for the year | (81) |  | (63) | 208
Income tax adjustments on prior years | 26 |  | (1) | 19
Change in tax rate | 0 |  | 0 | (38)
Deferred tax | (55) |  | (64) | 189
Income tax expense recognized in profit or loss | $ 8,122 | $ 289 | $ 7,946 | $ 6,405

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