How to modify child support or maintenance in Idaho

Sources last checked: 4 November 2026. Information only, not legal advice. The Cusp is not a law firm.

Idaho divorce kit How child support is calculated Alimony in Idaho Legal aid in Idaho After your divorce

The short version

Idaho uses the word “maintenance” for what other states call alimony. One statute, Idaho Code section 32-709, covers changing both maintenance and child support. A decree may be modified “only as to installments accruing subsequent to the motion for modification”, so a change cannot reach back before you file, and only on a showing of a substantial and material change of circumstances. The Idaho Supreme Court’s Court Assistance Office publishes a statewide Petition to Modify an Order, Judgment or Decree (CAO M 1-1), with instructions (CAO M Instruction 1). Both describe child support, custody and visitation changes. We found nothing on them about changing maintenance, so ask the Court Assistance Office in your county.

The test for child support

The wording below is a plain-language summary of the Idaho Code as published on the Legislature’s website on 4 November 2026, with short quotations.

The test, section 32-709(1): modification is allowed “only upon a showing of a substantial and material change of circumstances”.
Only for installments after the motion, 32-709(1): the decree can be changed “only as to installments accruing subsequent to the motion for modification”. Payments that came due before you filed are not changed by this section.
Guideline presumption, 32-706(5): the Legislature authorizes the Idaho Supreme Court to adopt child support guidelines. There is a “rebuttable presumption” that the guideline amount is the amount to be awarded, unless evidence shows that applying the guidelines “would be unjust or inappropriate”. A judge who departs must make a “written or specific finding on the record”.
Later-born children, 32-706(5): the statute tells the Supreme Court to provide that, on a modification, children of the party asking for it who were born or adopted after the existing order “shall not be considered”.
How long support lasts, 32-706(1) and (2): the court may order support until the child is eighteen. If the child is still in high school after turning eighteen, the court may continue it until the child stops school or reaches nineteen, whichever is sooner.
Withholding, 32-706(3): every child support order must tell the obligor that the order will be enforced by income withholding.
The court’s own form says: the petition reasons box lists the custodial arrangement, a parent’s gross annual income, medical insurance and the tax dependency exemption, and asks for the amount “based on the Idaho Child Support Guidelines”.

The test for maintenance

Same section, same test: section 32-709(1) refers to “any decree respecting maintenance or support”. So the substantial and material change test, and the rule limiting changes to installments after the motion, apply to maintenance as well.
What counts as a change: the statute does not define it. We read no court decisions, so we do not say how judges apply it.
Forms: see the next section. The petition we read has no section for maintenance.

How far back a change can reach, and arrears

Not before the motion: see 32-709(1) above. The court’s petition form lets you ask that new child support begin “the month after petition is filed” or the month after the judgment is signed. We did not read anything on which date judges choose.
Credit against arrears, 32-709(2): the court “may allow a credit against child support arrearages” for periods of more than 120 days during which the children lived primarily with the obligated parent with the custodial parent’s knowledge and consent.
Enforcement warning on the form instructions: they say that unpaid child support can lead to license suspension, and that the State Tax Commission will withhold and set off a state tax refund.

Forms and where to file

Where: section 32-715 gives the district court “Exclusive original jurisdiction” of divorce-chapter proceedings. The instructions say to use the county, judicial district, case number and names exactly as on the order you want to change.
If you disagree with the other parent: the instructions list the Petition to Modify an Order, Judgment or Decree, CAO M 1-1 (04/01/2018 on the form) and the Summons with Orders (CAO FL 1-3).
For child support, also: the Affidavit Verifying Income (CAO FL 1-11), a Child Support Worksheet (CAO FL 1-12 or 1-13), and the Child Support Transmittal Form (CSS 809). The instructions say a Court Assistance Officer can help produce the affidavit and worksheet.
If you both agree: a stipulation and a judgment of modification may be issued “without a hearing” and without the 21-day wait, using CAO M Instruction 2.
If the State of Idaho Department of Health and Welfare is a party: the instructions say to serve a Deputy Attorney General or the Department’s attorney of record, and point to a different form set (CAO GCSM Instruction 1).
Fee: the instructions say to give the clerk the appropriate filing fee or a fee waiver motion and affidavit (CAO FW 1-9 and 1-10). The court self-help site lists a $154 fee for a motion to reopen or modify a divorce and $166 for a child support case; ask the clerk which applies to you, because we could not confirm that. We state no amount.
Dates on the documents: the instructions are dated 07/01/2017 and the petition 04/01/2018. Ask the Court Assistance Office whether newer versions exist.

Notice, service and hearing

Service, three ways: the other party can sign an Acknowledgment of Service; or a sheriff, professional process server or other person over eighteen can serve the papers; or, if you do not know where the other parent is, you follow the separate publication instructions.
Time to respond: the other party has “twenty-one (21) days from the date of service to respond”. If there is no response you may apply for default and a judgment.
If the other party responds: if either party has asked for a change to child support, each must provide income information to the other “within 35 days from the day they filed the response”, using the Mandatory Child Support Disclosures form. A hearing ordinarily follows.
Final steps: the instructions call for a Judgment of Modification with the child support order attached, the transmittal form, and an appointment with the Court Assistance Office to review your papers before they go to the judge.

Before you file

Court staff cannot give legal advice. See legal aid in Idaho for free or low-cost help, or the Idaho divorce kit for the wider process. The instructions say you are held to the same standard as an attorney when you represent yourself.
Timing matters: because a change cannot reach back before the date of your motion, file as soon as your circumstances change.
The instructions also warn that if only a brief time has passed since the last order, the court may not grant the petition unless there was a clerical mistake or an emergency, and that the minimum time depends on the judge and other factors.
Child support amounts follow the state guidelines. See how child support is calculated in Idaho and alimony in Idaho. For other changes after a divorce, see After your divorce.

What we could not confirm

A form to modify maintenance. The petition and instructions we read cover child custody, visitation and child support. Ask the Court Assistance Office whether, and how, the petition is used for maintenance.
The meaning of a substantial and material change. The statute does not define it, and we read no court opinions.
Agreements. We did not read whether a settlement agreement can limit a later change to maintenance.
The guidelines themselves. We did not read the Idaho Rules of Family Law Procedure or the child support guidelines document, so we do not describe how the amount is calculated.
Filing fees and service costs. No dollar figure appears in the sources we read.
Current versions of the forms. The court self-help site still offered these same forms when we checked in November 2026, and the petition form itself carries a 04/01/2018 revision date. Older form dates are not a sign they are out of use, but check the court site for any newer version before you file.
The state child support agency. We did not read the Department of Health and Welfare’s pages, so this page does not describe a review through the agency.
Other maintenance statutes. We did not read the sections on how maintenance is first awarded or when it ends.

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