There are two types of support payments: child support and spousal support. While you can claim a tax deduction for spousal support payments made to your former spouse, you cannot claim child support payments that you have made. Likewise, your spouse does not include child support payments as taxable income in her tax return, but she must claim spousal support payments received. For example, if you paid your former spouse $5,000 in spousal support and $10,000 in child support, only claim a tax deduction for the spousal support payments you have made. Be sure to register your court order with the Canada Revenue Agency.
More details can be found in this TurboTax article: Divorce and Taxes