Parenting Days and the 110-Day Rule in Montana
In Montana, if the children spend 110 days or fewer a year with one parent, that parent pays his or her annual obligation in monthly payments; above 110 days each child’s obligation is reduced by 0.69% for each extra day and the parents’ amounts are offset.
The rule
If all the children of the calculation live primarily with one parent and spend no more than 110 days a year with the other, the annual transfer payment is the total annual support owed by the nonresidential parent, divided by the number of children and by 12 for each child (ARM 37.62.134(2)(a)).
Over 110 days
If any child spends more than 110 days a year with both parents, or children live primarily with each parent, the allocation changes: each child’s needs are recalculated, each parent’s total support is allocated per child, the part for time with the other parent is owed, and the two parents’ amounts are offset child by child; the parent with the higher total pays the difference (ARM 37.62.134(2)(b)).
The credit
On Worksheet B, for each parent the days over 110 are multiplied by a credit factor of 0.0069 (0.69% a day), applied to that parent’s obligation for the child. The difference between the two parents’ remaining amounts is paid by the parent with the higher amount, up to his or her own obligation.
Examples
The family in the worked example:
| Days with the fewer-days parent | Monthly payment |
|---|---|
| 0 days (all days with one parent) | $1,190 |
| 100 days | $1,190 |
| 130 days | $982 |
| 182 days (nearly equal) | $440 |
Up to 110 days the payment does not change; past 110 it falls as the days increase.
What a day is
A day is the majority of a 24-hour calendar period in which the child is with or under the control of a parent, unless the parents or the court define it differently (ARM 37.62.124). Disputed days may be divided equally.
Questions to bring to an attorney
Ask how the court will count the days and whether the schedule crosses the 110-day line.
Evidence to gather
The parenting plan, a calendar of the actual days and records of who has the children during school and child care.
Frequently asked questions
How do parenting days affect Montana child support?
Up to 110 days with the fewer-days parent no credit applies; above 110 a per-child credit and offset reduce the payment.
What is a parenting day in Montana?
The majority of a 24-hour calendar period with or under the control of a parent, midnight to midnight unless agreed.
Does Montana child support end at 50/50?
Not automatically: each parent's obligation is credited and the difference is paid by the parent with the higher amount.
Can the days differ by child in Montana?
Yes. The worksheets enter days for each child; this calculator uses the same number for all children.
What is the Montana credit factor?
0.0069 per day over 110, applied on Worksheet B.
Official sources
- Montana Child Support Guidelines Worksheets A to E and Instructions
- Montana Child Support Guidelines: ARM 37.62.101 to 37.62.148
- CSSD Policy 404.2 Guidelines Tables, effective February 1, 2026
A local family law attorney can review your situation — many offer a free consultation.
This is general information, not legal advice. It is based on the cited Montana statutes, rules and court opinions, and every case turns on its own facts. Confirm how the law applies to your situation with a licensed Montana attorney.