In Montana, the time a child spends with each parent changes child support only after a threshold is crossed. When a child lives primarily with one parent and spends no more than 110 days a year with the other, the guidelines make no adjustment. When a child spends more than 110 days a year with both parents, each parent's support amount is divided by days and the two are offset (ARM 37.62.124, 37.62.134). This page, part of our Montana Divorce Guide, explains the rule and why an equal schedule does not end support on its own.
The 110-Day Threshold
The rule reads: "When the child resides primarily with one parent and does not spend more than 110 days per year with the other parent, there is no adjustment to the transfer payment due. When at least one child spends more than 110 days per year with both parents, however, or when at least one child resides primarily with each parent, the transfer payment is adjusted" (ARM 37.62.124(2)).
| Arrangement | Effect on the payment | Rule |
|---|---|---|
| All children live primarily with one parent and spend 110 days or fewer per year with the other | No parenting-day adjustment. The transfer payment equals the other parent's total annual support amount. | ARM 37.62.124(2), 37.62.134(2)(a) |
| At least one child spends more than 110 days per year with both parents | Each parent's total is allocated by the child's days in each home, and the lower amount owed is subtracted from the higher. | ARM 37.62.134(2)(b) |
| One child lives primarily with one parent and another child lives primarily with the other | The same allocation and offset method applies, figured child by child. | ARM 37.62.134(2)(b) |
How a Day Is Counted
The guidelines define a day as "the majority of a 24-hour calendar period in which the child is with or under the control of a parent" (ARM 37.62.124(3)). Unless the parents agree otherwise or the court specifically finds otherwise, the period runs from midnight to midnight.
Time with a third party is assigned to a parent. When the child is at school or in day care, "the parent who is the primary contact for the third party is the parent who has control of the child for the period of third-party care." If both parents are primary contacts, or the parents cannot agree on the totals, the disputed days may be added up and divided equally between them.
The count starts from the parenting plan, which sets the child's residential schedule (ARM 37.62.124(1)). A plan that is specific about weekdays, weekends, holidays, and summers makes the count easier to agree on. See what a parenting plan must include.
How the Adjustment Works
Before days enter the picture, the guidelines have already produced a total annual support amount for each parent, based on income. Our page on how child support is calculated covers those steps. When the threshold is met, the rule then directs the following (ARM 37.62.134(2)(b)):
- Recalculate the needs of each child separately.
- Recombine each parent's total support amount for each child according to that child's proportionate need.
- Allocate each parent's amount for each child by "retaining the amount for time the child spends with the parent and owing to the other parent the amount for time the child spends with the other parent."
- Offset the two amounts by subtracting the lower obligation from the higher. The balance is the annual transfer payment for that child.
- Divide by 12 and round to whole dollars.
The Child Support Services Division's Worksheet B carries out these steps, and a copy of the worksheets must be attached to the order (ARM 37.62.148(3)).
Why Equal Time Does Not Mean Zero Support
Nothing in the guidelines sets support at zero for an equal schedule. The offset method compares what each parent owes the other. If both parents have about the same total support amount and the child is in each home half the year, the amounts each owes the other are close and the balance is small. If one parent's amount is larger, for example because that parent has more income available for support, that parent owes the difference.
That outcome follows from the purpose stated in the guidelines: a child's standard of living should not, to the degree possible, be adversely affected because the parents live in separate households (ARM 37.62.101(2)). A court that orders no support at all has to state its reasons (MCA § 40-4-204(3)(c)). For the parenting side of an equal schedule, see is 50/50 parenting the default.
Long-Distance Parenting
Distance is handled by a separate rule. A long distance parenting adjustment is allowed when travel by a parent or child to carry out the parenting plan exceeds 2,000 miles in a calendar year. The adjustment reduces that parent's income subject to the standard of living adjustment by the transportation cost above a standard amount. It is limited to transportation and does not include meals or lodging (ARM 37.62.130). If a move is being considered, our page on relocating with a child covers the parenting plan rules.
Keep Parenting Decisions About the Child
Because days affect dollars, parents sometimes find themselves arguing about a schedule when the real disagreement is about money, or the reverse. The two questions have different legal tests. A parenting plan is decided by the child's best interests, and support is then calculated from the schedule that results. A schedule proposed to reach a support number, and not because it suits the child, does not meet that test.
If the real schedule has drifted away from the written plan, the order does not change itself. Either the plan and the support order are amended, or the existing order continues to be owed. See modifying child support.
This page explains Montana law in general as of the 2025 Montana Code Annotated and the current Montana Child Support Guidelines. It is not legal advice about your specific case.