As per CRA (Canada Revenue Agency),
If you make child support payments for a child and the other parent does not, you cannot claim an amount for an eligible dependent for that child. Only the parent who does not pay child support can claim the amount for an eligible dependent on line 30400 of their tax return (Step 5 – Federal tax) for that child.
For full information view link below:
https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/suppor...
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