Yes, payment received as an executor of an estate is taxable income as see in this Canada Revenue Agency link. "Unless included in your business income, any trustee, executor, or liquidator fees paid to you for acting as an executor are income from an office or employment. As the executor, you must report these fees on a T4 slip.
For more information, see Employment by a trustee in Chapter 1 of the T4001, Employers' Guide - Payroll Deductions and Remittances."
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