Modifying Child Support in Minnesota

Last reviewed November 3, 2026

To modify child support in Minnesota, a parent must show that circumstances have changed enough to make the existing order unreasonable and unfair. The standard, the presumptions that help meet it, and the limits on retroactive relief all appear in Minn. Stat. § 518A.39. This page explains how a modification request is evaluated, how it is filed, and what a court will and will not consider. It is part of the site’s guide to child support in Minnesota.

The Legal Standard

A support order may be modified when one or more listed changes make its terms unreasonable and unfair (§ 518A.39, subd. 2(a)). The statute recognizes these grounds:

1. a significant rise or fall in the gross income of either parent;
2. a significant rise or fall in what either parent, or the child, needs;
3. the start of certain forms of public assistance;
4. cost-of-living changes reported by the federal Bureau of Labor Statistics;
5. extraordinary medical expenses of the child not otherwise provided for;
6. a change in the availability or cost of health care coverage;
7. new or substantially changed work-related or education-related child care expenses; and
8. the emancipation of a child.

Two elements must therefore be shown. First, a qualifying change must have occurred. Second, the change must make the current order unreasonable and unfair. Not every change in income satisfies both.

Presumptions That Help Meet the Standard

In several situations, the law presumes both elements (§ 518A.39, subd. 2(b)). The most frequently used is the 20 percent rule. Specifically, a substantial change is presumed when a new guideline calculation differs from the current order by at least 20 percent and at least $75 per month. If the current order is below $75, a 20 percent difference alone is enough.

Other presumptions apply when:

• the medical support provisions cannot be enforced;
• ordered health coverage is not available to the child;
• the order is stated as a percentage rather than a dollar amount;
• a parent’s gross income has fallen by at least 20 percent through no fault or choice of that parent; or
• a prior deviation for a child living in a foreign country no longer applies.

Each presumption is rebuttable. In other words, the other parent may still present evidence that the order remains fair.

Applying the 20 Percent Rule: An Illustration

Suppose a parent currently pays $600 per month in basic support. After that parent’s income drops, a new guideline calculation produces $470 per month. The difference is $130, which is about 22 percent of the current order. Because the change exceeds both 20 percent and $75, a substantial change is presumed.

By contrast, a new calculation of $540 would be a $60 change, or 10 percent. That meets neither threshold, so no presumption arises. The parent could still argue that the order is unreasonable and unfair, but without the statute’s help. The site’s worked child support example shows how a guideline calculation is performed.

Changes That Do Not, by Themselves, Justify Modification

Some events do not create a presumption on their own. For example, a parent’s responsibility for a new child born after the order is not, by itself, grounds for modification (§ 518A.39, subd. 2(c)). If other grounds exist, however, the court will then account for that child under § 518A.33.

A voluntary reduction in income is treated with caution as well. When a parent is voluntarily unemployed or underemployed, the court may calculate support using potential income instead (Minn. Stat. § 518A.32).

What the Court Considers

On a modification motion, the court applies the current guidelines in § 518A.35. The statute directs two further rules (§ 518A.39, subd. 2(e)):

• A new spouse’s finances are excluded. The court may not consider the income or resources of either parent’s spouse.
• Some extra work may be excluded. Compensation from work beyond a 40-hour week may be disregarded if it began after the existing order and is voluntary. The work must also be part-time or hourly overtime, among other conditions.

In addition, an older order may have used a different parenting time formula. In that event, the statute presumes that the prior adjustment continues unless the modification is based on a change in parenting time (§ 518A.39, subd. 2(d)).

Retroactivity: Why Timing Matters

As a rule, a modified amount cannot apply to any period before the other parent was served with the motion (§ 518A.39, subd. 2(f)). Where public assistance is involved, or the county attorney is the attorney of record, service on the county is also required. The parties may agree to a different effective date.

As a practical matter, a parent who delays filing generally cannot recover the difference for the months before service. Arrears that accrued under the old order usually remain owed.

How a Modification Is Filed

In the Expedited Child Support Process

When a county child support office is providing services, motions to modify are usually heard by a child support magistrate. They follow Minn. Gen. R. Prac. 372, which specifies the required forms, service, and filing. The motion must also be served on the county agency.

In District Court

Otherwise, the motion is brought in district court under the family court motion rules (Minn. Gen. R. Prac. 303). A support modification motion carries a $50 filing fee, which may be waived for a party who qualifies (Minn. Stat. § 357.021; § 563.01).

Supporting Documents

Either way, each parent must document income with a financial affidavit, recent pay stubs, and tax returns (Minn. Stat. § 518A.28). The site’s documents checklist lists the income records that are typically needed.

Adjustments That Do Not Require a Motion

Two changes occur without a modification motion. First, most orders include a cost-of-living adjustment every two years (Minn. Stat. § 518A.75). Second, support set as a specific amount per child generally ends automatically when that child emancipates (§ 518A.39, subd. 5). An order for two or more children stated as a single amount, however, continues in full until the youngest child emancipates or the court orders otherwise.

Modification Compared with Appeal

A modification looks forward from a change in circumstances. It does not correct an error in the original decision. A parent who believes the original order was wrong should consider the separate, time-limited process described in Appealing a Child Support Order. The broader framework appears in Minnesota Child Support.