New Mexico child support arrears accrue interest at 4% a year. That rate comes directly from Section 40-4-7.3 NMSA 1978. It is not the 8.75% general judgment rate that can apply to other judgments and to spousal support.
That distinction matters. Applying 8.75% to a child support balance would more than double the interest produced by the child-support statute. It also explains why a search for the general New Mexico judgment rate can lead to the wrong number for child support.
This article explains the law and payment order. To project principal over a period, open the New Mexico child support arrears calculator; for a case balance, use the official agency or court ledger.
Why 8.75% is not the child support rate
Two different rules are easy to mix up:
- Delinquent child support: 4% under Section 40-4-7.3.
- Spousal support: the rate set by Section 56-8-4 when the payment becomes due.
The child-support provision names 4% directly. It does not tell a reader to borrow the general judgment rate for child support. The cross-reference to Section 56-8-4 belongs to spousal support.
The 4% rule has been in the enacted text since 2004. Before relying on any online percentage, check whether the source is talking about child support, spousal support, or a general civil judgment. They are not interchangeable.
What happened to the proposed 6.5% rate?
A 2026 proposal, House Bill 266, would have increased the rate on delinquent child support from 4% to 6.5%. It did not become law. The New Mexico Legislature’s bill record marks HB 266 as died, with no votes and no final enacted version.
That means the proposal should not be used to calculate a current balance. A bill can supply useful context about what lawmakers considered, but introduced language does not replace the enacted statute.
When does New Mexico arrears interest start?
Interest starts when each support payment becomes delinquent. If an order, judgment, decree, or wage-withholding order does not specify a different due date, Section 40-4-7.3 says support is due on the first day of the month and becomes delinquent if it is not paid by that date.
This installment-by-installment rule is why a real agency ledger can differ from a quick estimate. Twelve missed monthly payments do not all age for twelve months. The oldest installment has accrued the longest; the newest has accrued for the shortest time.
For a defensible reconstruction, collect:
- Every payment due date and amount.
- Every payment received, with its posting date.
- Any change to the monthly order.
- Any consolidated judgment for delinquent support.
- The official agency or court ledger used in the case.
A simple 4% example
Suppose $10,000 of child support principal remained delinquent for one full year, with no payments, no new monthly obligations, and no other ledger events. A simple annual projection is:
| Starting principal | Rate | Illustrative interest | Projected total |
|---|---|---|---|
| $10,000 | 4% annually | $400 | $10,400 |
The calculation is $10,000 × 0.04 = $400. This example isolates the rate so it is easy to audit. It does not reproduce a real case with monthly due dates, partial payments, current support, or a consolidated judgment.
For your own balance, use the New Mexico child support arrears calculator. It applies the 4% rate as a projection and states its assumptions beside the result. Compare that estimate with the official ledger before making a payment or filing decision.
How New Mexico applies payments
Section 40-4-7.3 also sets an explicit application order. Support payments go to:
- The current support obligation.
- Delinquent support.
- The principal of a consolidated delinquent-support judgment.
- Accrued interest on delinquent support.
- Interest on the consolidated judgment.
So a payment does not necessarily reduce interest first. If current support and principal are still outstanding, they stand ahead of accrued interest in the statutory sequence. That ordering can make a balance decline differently from a consumer loan or credit card.
What the calculator can and cannot tell you
The calculator is useful for testing a principal balance, elapsed time, and the 4% rate. It is not a replacement for the dated accounting maintained by the New Mexico Child Support Services Division or the court.
Use the calculator to answer a planning question such as, “What would 4% produce on this principal over this period?” Use the official ledger to answer, “What amount is legally recorded as due today?” If those numbers differ, reconcile due dates, payment dates, allocation order, and any judgment event before assuming either figure is wrong.
Questions parents ask
What is the New Mexico child support arrears interest rate?
Section 40-4-7.3 NMSA 1978 sets interest on delinquent child support at 4% annually. The same 4% rate applies to a consolidated judgment for delinquent child support.
Is New Mexico child support interest 8.75%?
No. The child-support statute states 4% directly. The separate Section 56-8-4 judgment rate is referenced for spousal support, not delinquent child support.
Did New Mexico raise child support arrears interest to 6.5% in 2026?
No. House Bill 266 proposed a 6.5% rate, but the official legislative record marks the bill as died. The enacted 4% rule remains controlling.
When does interest begin on a missed New Mexico support payment?
Interest begins when the payment becomes delinquent. Unless the controlling order specifies another date, support is due on the first day of the month and is delinquent if unpaid then.
Estimate the balance at the correct rate
Open the New Mexico arrears calculator to model the statutory 4% rate. Keep the result as a planning estimate, then confirm every installment and payment against the official ledger.
