Basic Formula 1

• The basic formula, Formula 1, is used to calculate the annual rate of child support payable when only the parents have care of the child/ren and neither parent has another child support case
• The 8 Steps of the basic formula

  1. Child support income

  2. Combined child support income

  3. Income percentage

  4. Percentage of care

  5. Cost percentage

  6. Child support percentage

  7. Costs of the child

  8. Annual rate of child support for the child
• Relevant dependent child


  A parent's child (biological, adopted or the person's child pursuant to section 60H or section 60HB of the FL Act if the child was born as the result of an artificial conception procedure or as a result of a surrogacy arrangement) or, in certain limited circumstances, their step-child (section 5). The parent must have at least shared care of the child during the relevant care period.
• The child must be either under 18 years of age, have turned 18 and still be in secondary school and the last day of secondary school year has not yet occurred, and not be a member of a couple
• The parent must not be assessed in respect of the costs of the child. If the parent is assessed in respect of the costs of the child, then that child is included in the calculations as a multi-case child (section 47)
• In the case of a step-child, the parent has a duty to maintain that child by order of a court under FL Act section 66M or section 124 of the WA Family Court Act 1997
• If the parent does not have such an order, they may be able to apply for a change of assessment in special circumstances if his or her capacity to provide financial support for the child/ren of the assessment is significantly reduced because of the responsibility of the child support parent to maintain the step-child
• Other provisions of the Act may also be used to determine a parent's child support income, such as a change of assessment decision, a child support agreement, a court order, or a determination made under section 44 (post separation costs)
• Income percentage


  Each parent's income percentage is calculated by dividing the parent's child support income by the combined child support income and is rounded to 2 decimal places (section 55B). The income percentage indicates the share of the costs of a child a parent is responsible for meeting.
• Percentage of care


  A parent or non-parent carer's percentage of care is the percentage of care of the child the person is likely to have over the care period (sections 49-51)
• Cost percentage


  A parent's or non-parent carer's cost percentage represents the percentage of a child's costs the person meets directly through care. The cost percentage is determined according to the person's percentage of care, using the cost percentages table (section 55C).
• Child support percentage


  Each parent's child support percentage is worked out by subtracting the parent's cost percentage from their income percentage (section 55D(1)). A parent's child support percentage is taken to be nil if the amount worked out is negative (section 55D(2)).
• The costs of the child are determined by the parents' incomes, the number of children and the age of the children. The costs are calculated using the Costs of the Children Table, which is updated annually and used for child support periods starting within each calendar year.
• Annual rate of child support for the child

  Child support percentage × Costs of the child