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Usually IRA income is reported on line 115 and the final US tax paid is claimed as a foreign tax credit. The Canada Revenue Agency(CRA) has information on reporting IRA income:
Note: To support the claim for income tax required , CRA may ask for a US tax return to support the claim for the final tax paid.
In general if tax is paid to a foreign jurisdiction and not to Canada the claim on the tax return is for a foreign tax credit on the Canadian tax return
Like the link says you should likely contact CRA to get more information
Hope this helps