SupportDecode

Reviewed for current 2026 law

Montana Child Support Arrears Calculator

Model the department support-lien interest provision.

Reviewed by SupportDecode Editorial Team Page content reviewed Sources Methodology Update log

arrears calculator

Arrears owed

The unpaid support amount itself, before any interest.

Accrual period
How do you want to enter the period?

Estimated arrears with interest: $5,006.00

Interest of $6.00 at 0.12% compound per year (Mont. Code Ann. § 40-5-248(9)).

How this estimate was computed
Line itemAmount
Arrears principalMont. Code Ann. § 40-5-248 — support lien and interest (Montana Legislature)$5,000.00
Interest at 0.12% per year, compounded monthly, for 12 month(s) (Mont. Code Ann. § 40-5-248(9))The department may charge a support lien 1% monthly, compounded on the unpaid lien balance; this pack models that lien provision, not every private arrears ledger.Mont. Code Ann. § 40-5-248 — support lien and interest (Montana Legislature)$6.00
Arrears principal plus interestMont. Code Ann. § 40-5-248 — support lien and interest (Montana Legislature)$5,006.00

Assumptions

  • Accrual period expressed as 12 month(s); partial months prorate.
  • Compounding applied monthly at one-twelfth of the annual rate.

Estimate only. The court or state agency calculation controls.

Montana arrears interest under Mont. Code Ann. § 40-5-248(9); rules last reviewed 2026-08-09.

A CSSD lien may carry 1% monthly interest

Section 40-5-248 permits the department to charge one percent each month on a support lien.

The monthly calculation includes previously accrued interest and may be waived to facilitate collection.

Rate
1% monthlysource
Method
Monthly compoundsource
Scope
Department support liensource

Confirm a lien and interest election

Do not apply this result automatically to every private arrears balance.

What this estimate includes

  • Monthly compounded lien estimate

What it leaves out

  • Private judgment-rate lookup
  • Waiver decision
  • Dated payment ledger

Montana arrears calculator FAQs

Does the lien rate compound?

Yes, the statute includes prior accrued interest in the month-end unpaid balance.

Is it mandatory?

The statute says the department may charge it.

Can interest be waived?

Yes, if waiver would facilitate collection.

Does every private balance use 1% monthly?

Not necessarily; this page models the support-lien provision.

When does it accrue?

At the close of the last business day of each month.

Should I request a ledger?

Yes.

Official sources

Official sources last verified: .

Changelog: page reviewed . Material changes appear in the update log.