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New Hampshire child support: the RSA 458-C percentages, shared schedules, and a worked example

New Hampshire writes its formula into statute as a sliding table of percentages: the share of combined net income devoted to children falls as income rises. Since January 1, 2025 the law also says when equal or shared parenting schedules should lower support, including a presumption of $0 for parents with similar incomes.

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At a glance

ModelPercentage of combined net income, divided by income (RSA 458-C:3)
PercentagesTwo children: 35.5% at $15,000 a year of combined net income, sliding to 27.5% at $100,000 and 26% at $125,000 or more
Shared parentingOver 40% each with incomes within 10%: $0 presumed; over 35% each: deviation considered
Medical supportPresumed reasonable at 4% of each parent's gross income
Low incomeSelf-support reserve of 130% of the federal poverty guideline; $50 a month minimum order
Support endsAge 18, or high school graduation or 2 months past 19 (whichever first) for a full-time student
ModificationAfter 3 years without showing a change, or any time on a substantial change

From gross income to the percentage table

Gross income includes nearly everything: wages, commissions, tips, self-employment and business income, rents, interest and dividends, alimony, pensions, Social Security, unemployment, workers' compensation and veterans' benefits, even lottery winnings. Public assistance such as SSI and food stamps is excluded. So is occasional or seasonal hourly overtime above 40 hours a week in trades that commonly pay overtime, a carve-out that does not apply to professionals or business owners who control their own pay. A new spouse's income is counted only if the parent quit or refused work.

Adjusted gross income subtracts support actually paid to others, half of self-employment tax, mandatory retirement contributions, state income taxes actually paid, and what the paying parent spends on child care or medical support for these children. Net income then subtracts standard federal income tax and FICA amounts published each year by the Department of Health and Human Services.

The statute's table sets the percentage for each income level and number of children, and DHHS publishes the resulting schedule with interpolated percentages between the listed incomes. The total obligation is divided between the parents in proportion to income, rounded to the whole dollar.

Worked example: New Hampshire

  1. Parent A has $5,000 a month in net income and Parent B $3,333, for $8,333 a month, exactly $100,000 a year combined.
  2. At $100,000 the statute's percentage for two children is 27.5%, so the total support obligation is $27,500 a year, or $2,292 a month.
  3. Parent A has 60% of the combined net income. With the children living mainly with Parent B, Parent A owes $1,375 a month, $16,500 a year.
  4. CoreParent's calculator applies the statute's percentages and self-support reserve, but it estimates net income from gross pay instead of using the DHHS standard deductions, so its number can differ from the DHHS calculator.

This is an estimate, not legal advice. Figures are rounded to the dollar and leave out the insurance, childcare, and other adjustments your case may have. Try your own numbers in CoreParent's calculator, then confirm with the state's official calculator.

The 2025 parenting schedule rules

New Hampshire defines an approximately equal parenting schedule as more than 40% of the time with each parent, a substantially shared schedule as more than 35%, and substantially similar incomes as gross monthly incomes no more than 10% apart. When the parents split child care, uninsured medical costs and agreed activities 50/50, the law presumes $0 support for similar incomes on an approximately equal schedule, and a deviation for similar incomes on a substantially shared one.

With different incomes, the guideline amount may or may not fit; the court asks whether the lower earner can meet the children's costs in a similar style. In any shared schedule without extraordinary circumstances, support should not leave the receiving parent with more income than the paying parent. In the example, that ceiling brings Parent A's $1,375 down to about $833 a month. These presumptions can be set aside for reasons like a child's serious health needs, long distances, unpredictable work schedules or abuse.

Medical support and child care

The court sets a medical support obligation for each parent, presumed reasonable at 4% of that parent's gross income unless it finds that amount unjust. Allowable work-related child care, including necessary work-related education and training, is handled by deducting it from the income of the parent who pays it before the shares are computed, so it shifts the split rather than being added on top.

Low income: the reserve and the $50 order

The self-support reserve is 130% of the federal poverty guideline for one person. If the paying parent's gross income is below it and the parent is not voluntarily unemployed, the order is the $50 monthly minimum, or less if the court finds that appropriate. If paying the full amount would push the parent's adjusted income below the reserve, support is the amount above the reserve, but never under $50. Incarceration is never treated as voluntary unemployment.

Other special circumstances

Besides the parenting schedule, a court may adjust for extraordinary medical, dental or education costs, very high or very low incomes, stepchildren and other children, the paying parent's reasonable costs of parenting time, the disposition of the marital home, tax consequences and dependency exemptions, and voluntary or ordered college costs. The party asking must prove the circumstance, and the court must make written findings.

When support ends

Support ends when the child marries, joins the armed services, is emancipated by court order, or turns 18. A child still in elementary, secondary, charter or approved home school full time at 18 keeps support until graduation or two months after turning 19, whichever comes first, and it then ends without further court action. For a child with disabilities, support may continue, but orders effective after July 9, 2013 end by 21. A support order cannot require contribution to college costs, except as RSA 461-A:21 allows.

Modification

Either parent can ask for a modification three years after the last support order without proving any change, or at any time on a substantial change of circumstances. When one of several children ages out, that is a substantial change. A modification cannot take effect before the other parent received notice of the petition.

The state agency

The Bureau of Child Support Services at the New Hampshire Department of Health and Human Services establishes and enforces orders, publishes the guideline table and calculator, and must review the guidelines at least every four years. All support orders provide for wage assignment.

Documents you will need

New Hampshire child support FAQ

What percentage is child support in New Hampshire?

It depends on combined net income and the number of children. For two children the statute sets 35.5% at $15,000 a year, 27.5% at $100,000 and 26% at $125,000 or more, with DHHS interpolating in between.

Is there child support with 50/50 custody in New Hampshire?

If each parent has more than 40% of the time, incomes are within 10%, and costs are split 50/50, $0 is presumed. With different incomes, support should not leave the receiving parent with more income than the payer; about $833 a month in our example.

How much is child support for 2 kids in New Hampshire?

At $100,000 a year of combined net income it is 27.5%, $2,292 a month in total. A parent with 60% of the income pays about $1,375.

When does child support end in New Hampshire?

At 18, or for a full-time student still in high school, at graduation or two months after turning 19, whichever comes first.

How often can New Hampshire child support be modified?

Every three years without showing a change, or sooner with a substantial change of circumstances.

Next steps

Sources

Verified against these official sources in October 2026:

Child support in every other state

All states

This is general educational information, not legal advice, and official figures change. Last verified: October 2026. Consult a licensed family-law attorney in New Hampshire.