Quick answer: Montana child support interest: we could not verify a fixed rate for support arrears. General judgments carry prime plus 3%, simple, but sources disagree on support. Support is delinquent 8 working days after month end, and a license can be suspended at 6 months of arrears after 60 days’ notice.
This Montana child support arrears calculator adds up the unpaid installments, lets you test an interest rate and flags the withholding, license and passport thresholds under MCA 40-5-412. Interest defaults to zero.
Montana child support arrears and interest at a glance
| Rule | What Montana says |
|---|---|
| Delinquent | 8 working days after the last day of the month in which the payment is due (MCA 40-5-412(1)(b)) |
| Withholding | Immediate for most orders unless an exception is written in; otherwise from the day the obligor becomes delinquent (40-5-411; 40-5-412) |
| Licenses | A delinquency of at least 6 months of support at service of notice; 60 days to pay, agree to a payment plan or request a hearing (40-5-701(3); 40-5-702) |
| Security | On a showing of a 6-month delinquency the court can order bond, a mortgage or other security of up to 2 years of support (40-4-209) |
| Judgment interest | General judgments: prime plus 3%, set each January 1, not compounded (25-9-205); we could not verify its use on support arrears |
| Retroactive changes | Only from actual notice of a motion (40-4-208(1)) |
How do child support arrears work in Montana?
- Interest and what we could not verify. See what the Montana statutes say about interest on child support.
- Collection. See what happens if you do not pay child support in Montana.
- Time limits and forgiveness. See whether Montana child support arrears expire or can be forgiven.
What does this arrears calculator check?
You enter the monthly support and the number of installments unpaid, and optionally an annual rate to test. The calculator adds simple interest from each due date only if you enter a rate, and flags the delinquency, 6-month license and $2,500 passport triggers. It does not model partial payments. To change the amount going forward, see the Montana child support modification calculator, and for when the obligation stops, the Montana child support end date calculator.
Frequently asked questions
Does Montana charge interest on child support arrears?
We could not verify a fixed rate for support arrears. General court judgments carry prime plus 3%, simple, but sources disagree on support, so ask the court or the department.
When is a Montana child support payment delinquent?
Eight working days after the last day of the month in which the payment is due.
When can a Montana license be suspended for unpaid child support?
When the delinquency is at least 6 months of support at service of the notice; the notice gives 60 days to pay, agree to a plan or request a hearing.
How does Montana start income withholding for delinquent support?
The department can notify the obligor that withholding will start if the delinquent amount is not received within 8 days, then send an order to the employer.
Can Montana require a bond for unpaid child support?
Yes, after a showing of a delinquency of 6 months of support, up to two years of support.
Official sources
- MCA 40-5-412: delinquency income withholding
- MCA 40-5-411: immediate income withholding
- MCA 40-5-701: license suspension definitions
- MCA 40-5-702: notice of intent to suspend
- MCA 40-5-704: suspension of licenses
- MCA 25-9-205: interest on judgments
- MCA 40-4-208: modification
- 15 U.S.C. 1673: restriction on garnishment
- 42 U.S.C. 652(k): denial of passports