Quoting from the link provided below:
"If you were separated from your spouse or common-law partner during the tax year because of a breakdown in your relationship, or if you share custody of your dependant child with the child’s other parent:
- If you made support payments for the dependant during the tax year, you can claim the amount for an eligible dependant only if you don’t claim the support payments you made to your spouse or common-law partner during the tax year on your return. You can choose whichever option is best for you.
- You cannot claim the amount for an eligible dependant if you received support payments for the dependant.
- If you and another parent share custody of the dependant, or if you both make support payments, only one of you can make the claim. If you and the other person(s) making support payments cannot agree on who will claim the amount, neither parent may claim the amount. In this case, if you’re claiming the dependant, do not include the support payments you made on your return (but do include support payments you received).
- Only one parent can claim the amount for the child. You cannot split the amount with the other parent."
Please review this FAQ from TurboTax for more information.
Also, this article will explain more details.
