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Income taxes (Tables) | 12 Months Ended
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Sep. 30, 2025
Income Taxes [Abstract] |
Disclosure of income tax expense |
| Year ended September 30
| 2025 | 2024
| $ | $
Current income tax expense |  |
Current income tax expense in respect of the current year | 628,169 |  | 731,338 |
Adjustments recognized in the current year in relation to the income tax (recovery) expense of prior years | (44,889) |  | 12,998 |
Total current income tax expense | 583,280 |  | 744,336 |
Deferred income tax expense (recovery) |  |
Deferred income tax recovery relating to the origination and reversal of temporary differences | (33,531) |  | (118,893) |
Deferred income tax recovery relating to changes in tax rates | (1,619) |  | — |
Adjustments recognized in the current year in relation to the deferred income tax expense (recovery) of prior years | 35,775 |  | (27,207) |
Total deferred income tax expense (recovery) | 625 |  | (146,100) |
Total income tax expense | 583,905 |  | 598,236 |
Reconciliation of effective income tax rate from the combined federal and provincial canadian statutory tax rate | The Company’s effective income tax rate differs from the combined Federal and Provincial Canadian statutory tax rate as follows:
| Year ended September 30
| 2025 | 2024
| % | %
Company's statutory tax rate | 26.5 |  | 26.5 |
Effect of foreign tax rate differences | (0.7) |  | (0.3) |
Final determination from agreements with tax authorities and expirations of statutes of limitations | (0.4) |  | (0.3) |
Non-deductible and tax exempt items | 0.5 |  | 0.3 |
Recognition of previously unrecognized temporary differences | — |  | (0.3) |
Minimum income tax charge | 0.2 |  | 0.2 |
Changes in tax laws and rates | (0.1) |  | — |
Effective income tax rate | 26.0 |  | 26.1 |
Disclosure of continuity of deferred tax balance | The continuity schedule of deferred tax balances is as follows:
| As at September 30, 2024 | Additions from business acquisitions | Recognized in earnings | Recognized in other comprehensive income | Recognized in equity | Foreign currency translation adjustment and other | As at September 30, 2025
| $ | $ | $ | $ | $ | $ | $
Accounts payable, accrued compensation and liabilities, provisions, and other long-term liabilities | 132,021 |  | — |  | (13,894) |  | — |  | (5,811) |  | 3,933 |  | 116,249 |
Tax benefits on losses carried forward | 51,180 |  | — |  | 618 |  | — |  | — |  | 2,164 |  | 53,962 |
Retirement benefits obligations | 27,034 |  | — |  | 2,297 |  | (13,062) |  | — |  | 2,125 |  | 18,394 |
Capitalized research and development | 174,467 |  | — |  | 18,545 |  | — |  | — |  | 5,370 |  | 198,382 |
Lease liabilities | 156,479 |  | 4,360 |  | (712) |  | — |  | — |  | 7,925 |  | 168,052 |
PP&E, contract costs, intangible assets and other long-term assets | (73,149) |  | (44,860) |  | (4,353) |  | — |  | — |  | (4,801) |  | (127,163) |
Right-of-use assets | (123,982) |  | (4,360) |  | 3,237 |  | — |  | — |  | (6,800) |  | (131,905) |
Work in progress | (15,621) |  | — |  | (3,593) |  | — |  | — |  | (857) |  | (20,071) |
Goodwill | (93,682) |  | — |  | (20,157) |  | — |  | — |  | (2,949) |  | (116,788) |
Refundable tax credits on salaries | (24,943) |  | (532) |  | 6,257 |  | — |  | — |  | (25) |  | (19,243) |
Cash flow and net investment hedges | 14,060 |  | — |  | 26 |  | 5,873 |  | — |  | 294 |  | 20,253 |
Other | (2,429) |  | — |  | 11,103 |  | (285) |  | — |  | (900) |  | 7,489 |
Deferred taxes, net | 221,435 |  | (45,392) |  | (626) |  | (7,474) |  | (5,811) |  | 5,479 |  | 167,611 |
| As at September 30, 2023 |  | Additions from business acquisitions | Recognized in earnings | Recognized in other comprehensive income | Recognized in equity | Foreign currency translation adjustment and other | As at September 30, 2024
| $ |  | $ | $ | $ | $ | $ | $
Accounts payable, accrued compensation and liabilities, provisions, and other long-term liabilities | 112,599 |  |  | — |  | 20,946 |  | — |  | (3,599) |  | 2,075 |  | 132,021 |
Tax benefits on losses carried forward | 56,078 |  |  | — |  | (7,265) |  | — |  | — |  | 2,367 |  | 51,180 |
Retirement benefits obligations | 27,243 |  |  | — |  | 795 |  | (356) |  | — |  | (648) |  | 27,034 |
Capitalized research and development | 92,880 |  |  | — |  | 82,302 |  | — |  | — |  | (715) |  | 174,467 |
Lease liabilities | 169,288 |  |  | — |  | (16,919) |  | — |  | — |  | 4,110 |  | 156,479 |
PP&E, contract costs, intangible assets and other long-term assets | (123,717) |  |  | — |  | 49,457 |  | — |  | — |  | 1,111 |  | (73,149) |
Right-of-use assets | (143,411) |  |  | — |  | 23,077 |  | — |  | — |  | (3,648) |  | (123,982) |
Work in progress | (14,372) |  |  | — |  | (926) |  | — |  | — |  | (323) |  | (15,621) |
Goodwill | (87,259) |  |  | — |  | (6,346) |  | — |  | — |  | (77) |  | (93,682) |
Refundable tax credits on salaries | (22,568) |  |  | — |  | (2,478) |  | — |  | — |  | 103 |  | (24,943) |
Cash flow and net investment hedges | (4,010) |  |  | — |  | 14,164 |  | 5,374 |  | — |  | (1,468) |  | 14,060 |
Other | 11,600 |  |  | — |  | (10,707) |  | (3,462) |  | — |  | 140 |  | (2,429) |
Deferred taxes, net | 74,351 |  |  | — |  | 146,100 |  | 1,556 |  | (3,599) |  | 3,027 |  | 221,435 |
16. Income taxes (continued) The deferred tax balances are presented as follows in the consolidated balance sheets:
| As at September 30, 2025 | As at September 30, 2024
| $ | $
Deferred tax assets | 239,284 |  | 242,567 |
Deferred tax liabilities | (71,673) |  | (21,132) |
| 167,611 |  | 221,435 |

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