Once you and the other parent have agreed where the children will live and for how much of the time, you can begin to work out a fair amount of child support. Depending on the parenting arrangement, it will be important to know what one or both parents earn in a year.

How do we calculate annual income?

To figure out child support you will have to know what the paying parent earns in a year – before the government taxes were taken off. This is “gross annual income.” The paying parent’s annual income can be figured out by:

• Using the amount on line 150 on your income tax return (or notice of assessment from the Canada Revenue Agency), and then minus any union dues from that amount
• Looking at your pay stubs for a full year and adding up what you were paid each month (before all the taxes were taken off)

How do we calculate child support when the children live mostly with one parent?

The parent who has the children most of the time will receive child support. The parent who doesn’t have the children most of the time is the paying parent.

Once you know how much the paying parent earns in a year, the easiest way to work out the basic amount of child support is to use the online calculator at the Child Support Lookup.

To find out monthly child support payments using the calculator, follow these steps:

• Enter the annual income before taxes of the paying parent (which you figured out above)
• Enter the number of children involved
• Select the province where the paying parent lives
• Click on the “Lookup” button
• The monthly amount is displayed immediately in blue text

The online calculator follows the Child Support Tables, which were created by the federal government so that parents know what is fair according to the law. The Tables are based on what an average parent at each income level would usually spend on their children, if the parents were still together. However, this is only the basic amount of child support. Parents who have separated also have to calculate other types of expenses, which are known as special and extraordinary expenses.

How do we calculate child support when parenting is shared?

A shared parenting arrangement is when the children live about the same amount of time with each of their parents over the course of a year. That means at least 40% of the time with each parent. If you agree that each of you has the children for about the same amount of time, the paying parent is usually the one who makes the most money.

To figure out the amount of child support for a shared parenting arrangement, you start by putting the gross annual income of each parent into the Child Support Online Lookup, which is an online calculator. If you aren’t sure how to figure out “annual gross income,” see "How do we calculate annual income?" above. Once you find out the child support monthly payments (as if each of you were the “paying parent”), then you subtract the lower amount from the higher amount.

The difference in the two amounts is what the higher income earner has to pay to the other parent. Here’s an example of how to do it:

Parents who have separated also have to calculate other types of expenses, which are known as special and extraordinary expenses.

In a shared custody arrangement parents may decide to base child support not just on the Table amount each would pay. Parents can also take into account any increased costs of shared custody (like both parents having to maintain a household for the children) and the conditions, means, needs and other circumstances of both the parents and the children.

How do we calculate child support when parenting is split?

A split parenting arrangement is when there are two or more children and each parent provides primary care for one or more of the children, which means:

• One or more children live with one parent most of the time (more than 60% of the time in the year), and
• One or more children live with the other parent most of the time (more than 60% of the time in the year).

To calculate child support in the case of a split parenting arrangement, the first step is for each parent to use the Child Support Online Lookup as if they each had to pay child support. They would enter their annual income (see "How do we calculate annual income?" above), and the number of children who live with the other parent. The paying parent will be whoever has to pay more according to the child support calculator. However, the amount that parent has to pay is the difference between the two amounts they got for each parent. Here’s an example of how to do it:

Parents who have separated also have to calculate other types of expenses, which are known as special and extraordinary expenses.

How do we calculate other types of expenses for the children?

Under the Child Support Guidelines each parent is expected to contribute to special and extraordinary expenses related to the child. Special and extraordinary expenses go above and beyond what child support itself covers and should also be included in your child support agreement.

Special and extraordinary expenses are defined as:

• Necessary — because they are in the children’s best interests, and
• Reasonable — because they take into consideration how much the parents earn and what the family's spending patterns were before the separation.

Special and extraordinary expenses include the following:

• Child-care expenses that a parent with whom the children live faces as a result of the parent's job, illness, disability or educational requirements for employment.
• The portion of a parent's medical and dental insurance premiums that provides coverage for the children.
• The children’s healthcare needs over and above that covered by insurance (for example, orthodontics, counselling, medication, eye care and other items) that exceed $100 per year.
• The children’s extraordinary expenses for extracurricular activities.
• The children’s extraordinary expenses for primary and secondary education or other educational programs.
• The children’s expenses for post-secondary education.

You and the other parent are free to decide which expenses are reasonable and necessary. Once you do that, you can decide how much each of you will contribute to them. As a general rule, you would share the cost in proportion to your incomes, but you may agree to another arrangement.

To share expenses in proportion to your incomes means each of you pay a portion of the cost — a percentage amount — equal to what you earn. For example, if both parents have the same income, they would each pay for one-half (50%) of the cost of the activity. Here’s an example of how to do the calculation if you don’t earn the same amount:

Keep in mind that special and extraordinary expenses have to be reasonable based on the parents’ financial situation and the children’s needs.

What should we do once we agree on an amount?

Once you and the other parent agree on an amount of child support, including special and extraordinary expenses, you should:

• Write up the details of your agreement
• Each sign it — with two different witnesses watching each of you sign
• Ask the witnesses to sign the document
• Put it in a safe place

You and the other parent should continue to talk about child support at least once a year. If there are any changes in either parent’s income, you should discuss whether the current child support amounts you agreed to are still covering the costs of raising the children.