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 are 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 (see "How do we calculate annual income?" 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 Guidelines, which were created by the federal government so that parents know what is fair according to the law. The guidelines 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. This includes expenses for daycare and extracurricular activities live sports or music lessons.

How do we calculate child support when parenting is shared?

Shared custody 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. Just because the paying parent has the children for 40% or more of the time does not mean they don’t pay child support.

To figure out the amount of child support for a shared custody 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 split the difference between those two amounts.

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. This includes expenses for daycare and extracurricular activities like sports or music lessons.

How do we calculate child support when parenting is split?

Split custody 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, and
• One or more children live with the other parent most of the time.

To figure out the amount of child support for a split custody 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 split the difference between those two amounts.

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. This includes expenses for daycare and extracurricular activities like sports or music lessons.

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

Before you agree on a final amount of child support, consider all of the other costs of raising your children. These are called special and extraordinary expenses. These types of expenses are not included in the basic child support amounts that you get if you use the online calculator. They 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 — in relation to the family’s financial circumstances, taking into consideration how much the parents earn and what the family's spending patterns were before the separation.

Special and extraordinary expenses can 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).
• The children’s expenses for extracurricular activities, such as sports or musical lessons.
• The children’s 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
• Have a lawyer review it
• 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
• Ask the staff at court to “file” it

You don’t have to file your child support agreement at the court. So long as your agreement follows the Child Support Guidelines, it is a valid document. You are only required to file your agreement in court if:

• You want to enroll with the Family Responsibility Office (FRO), or
• The paying parent hasn’t been paying the child support amount you agreed to and you need to go to court to get your agreement enforced or a child support order

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.