1. As a biological parent, child support is determined pursuant to the Child Support Guidelines and is calculated using your gross annual income. For most people, that’s your ‘Line 150’ income on your income tax return. You can easily input that number along with the number of children you have into this calculator to learn what your child support obligations are going to be.
2. As a stepparent, you can in fact be liable to pay child support for your ex spouse’s child(ren). This is not an automatic responsibility like child support for biological children, but can be ordered if you assumed the role of a parent and contributed to their upbringing financially. Any obligation you have is secondary to the biological parents. As a stepparent, the amount of child support may vary from the Guideline amount, and it’s best to speak to a lawyer to determine what range you could be looking at paying. The court considers things like the child(ren)’s standard of living and the length of time you were involved in their life when determining payments.
3. Don’t think you can avoid child support by quitting your job. While that sounds like it would solve all manner of problems, it’s actually the equivalent of wearing Groucho glasses and hoping your ex won’t recognize you in court (where she will surely be taking you if you don’t pay your child support). Courts will figure out that you’re intentionally unemployed, or underemployed, or hiding, and impute an income to you based on what you are capable of earning, not what you’re actually earning, when calculating your payments for you.If you share parenting time of your kids pretty much equally with your ex (you have them at least 40% of the time), or if you each care for one child, you and your spouse will likely be ordered to pay child support to each other, with the higher earner simply paying the “offset” amount to the lower earner. There are tax implications to this, so it’s important to speak to a lawyer and accountant about how to put this into an order or an agreement.
4. You and your ex cannot negotiate out of paying each other child support. Child support is the right of the child(ren), and it is paid to the primary parent in order to care for them. You may not be permitted to finalize your divorce until you’ve made suitable arrangements for the financial care your child(ren).
5. Child support is not tax deductible for the payer or taxable income for the recipient. Having said that, there are important tax considerations to how your order or agreement is worded and structured. It is important that you speak to a lawyer and accountant about these issues before finalizing your documents. You can read more about tax implications for separation here.
6. If you’re having trouble collecting child support from your ex pursuant to an order or agreement, consider enrolling with the Family Maintenance Enforcement Program (FMEP). They have the ability to garnish her wages, intercept government payments like tax returns and GST cheques, and can even suspend her driver’s licence or passport or throw her in jail (true story).
7. The income of your ex-wife’s new man is likely irrelevant when it comes to calculating the child support you are required to pay, even if he earns double what you make. Of course as with everything related to law, there can be exceptions. There is case law to suggest that the income of a new partner may come into consideration for “special and extraordinary” or “s.7” expenses.
8. It’s possible to lower your monthly child support amount if you can convince a court you would suffer an “undue hardship” by having to pay the allotted amount. Proving this is akin to learning a foreign language at the same time as learning to fly a plane, in other words, it is a difficult task. Possible reasons can be the result of you taking responsible for sizeable family debts from the relationship, unreasonably high cost required to exercise your parenting time with your children, or a legal obligation to support another child or dependent. For more information, check out this case. This can be a complex area of the law and difficult argument to make, so it is important that you get some legal advice before pursuing this.
9. If you earn more than $150,000 per year, you may have the ability to argue that the Guideline table amount is unreasonable, and pursue a smaller amount be ordered. The courts tend to order the Guideline amount for incomes close to the $150,000 amount, but once you get into incomes of $500,000+, the courts will sometimes stray from the guideline amount. To learn more about this, you can read about the leading case on this issue here.
10. Bonus tip! In addition to monthly child support payments, you could also be required to share the cost of little Billy’s hockey fees, tutoring or braces. These things may be considered special and extraordinary expenses under the Child Support Guidelines (section 7).

Caution: This is not legal advice, and you should not rely on it as such. To ensure your interests are protected, formally seek advice from a lawyer.