New Hampshire Child Support Guidelines: How Support Is Calculated

In New Hampshire, child support is set using a statutory guideline formula: the parents' combined net income is multiplied by a percentage that depends on how many children are covered, and the resulting total obligation is then divided between the parents in proportion to each parent's share of that combined income (RSA 458-C:3). The percentage isn't fixed — it slides based on how much combined income there is, and it can be adjusted up or down for "special circumstances," reduced to a bare minimum for very low-income parents, or pushed toward zero when parents share parenting time close to equally. The sections below walk through each moving part.

The basic formula

New Hampshire's guideline applies a percentage of combined net income based on the number of children the order covers. At combined net income of $15,000 or less, the guideline percentages run about:

• 25.6% for one child
• 35.5% for two children
• 42.5% for three children
• 45% for four or more children

Those percentages slide downward as combined net income rises, dropping to roughly 19% / 26% / 31% / 33.5% (for one, two, three, and four-or-more children, respectively) once combined net income reaches $125,000 or more. In between, the percentage is somewhere on that sliding scale (RSA 458-C:3). Whatever the applicable percentage produces as the total support obligation, each parent then pays their proportional share based on their own share of the parents' combined net income.

What counts as income

The formula starts from gross income, which New Hampshire defines broadly: wages, salary, commissions, tips, self-employment income, interest, dividends, trust income, annuities, pensions, Social Security, workers' compensation, unemployment, disability, veterans' benefits, and even gambling or lottery winnings all count. There's a narrow carve-out for certain overtime pay above 40 hours a week for hourly workers in traditionally overtime-eligible industries, which is excluded (RSA 458-C:2, IV).

From gross income, the state calculates adjusted gross income by subtracting: court- or administratively-ordered support actually paid to others, 50% of self-employment tax actually paid, mandatory (not voluntary) retirement contributions, actual state income taxes paid, and the children's allowable child-care and medical-support costs. From there, net income is calculated by further deducting federal income tax, F.I.C.A., and Medicare, using IRS withholding tables (RSA 458-C:2, I and RSA 458-C:2, VI).

Time-sensitive: shared parenting schedules can zero out or reduce support

This rule applies to orders issued on or after January 1, 2025 — if your order predates that, ask the court which version of the rule applies to you. Under the current rule, an "approximately equal" parenting schedule means each parent has more than 40% of the annual parenting-time schedule, and a "substantially shared" schedule means each parent has more than 35%. Where the parents' incomes are substantially similar:

• An approximately equal schedule creates a rebuttable presumption of a $0 support obligation.
• A substantially shared schedule creates a rebuttable presumption that the court should deviate from the standard guideline amount.

Both are presumptions, not automatic outcomes — either parent can present evidence to the court to rebut them (RSA 458-C:5, I(h) and RSA 458-C:2, VIII-c).

Minimum orders and low-income parents

New Hampshire builds in a floor for parents with little or no income. The self-support reserve is set at 130% of the federal poverty guideline for a single person living alone. If a parent's income falls below that reserve and the parent isn't voluntarily unemployed or underemployed, the court orders only the minimum support amount — generally $50 per month, unless the court determines a lesser amount is appropriate (RSA 458-C:2, V; RSA 458-C:2, X; RSA 458-C:3, IV).

When the court can deviate from the guideline

The guideline amount isn't always the final number. A parent can ask the court to deviate by proving, by a preponderance of the evidence, that special circumstances apply. New Hampshire law lists examples including (but not limited to):

• Ongoing extraordinary medical, dental, or education expenses
• Significantly high or significantly low income
• The economic impact of stepchildren in the household
• The costs of exercising parenting time
• Disposition of the marital home
• Tax consequences of the support arrangement
• Other special circumstances the court finds relevant

If the court applies any of these, it must make written findings explaining why (RSA 458-C:5, I).

Modifying an existing order

You don't have to prove your circumstances changed if enough time has passed: either parent may ask the court to modify a support order three years after the entry of the last support order without showing a substantial change of circumstances. Before that three-year mark, you generally need to show a substantial change of circumstances to modify. Either way, a modification only takes effect after the other parent (the respondent) has been given notice of the modification petition — it isn't automatic or retroactive to before notice (RSA 458-C:7).

Enforcement, including across state lines

Child support in New Hampshire is backed by a federal enforcement structure. Under the federal Title IV-D program, states must run a child-support enforcement agency and use standardized tools such as income withholding, paternity establishment, license suspension, and liens (42 U.S.C. §§ 654, 666); federal law also waives sovereign immunity so federal wages and benefits can be garnished to pay support (42 U.S.C. § 659).

If one parent lives out of state, a separate federal statute requires every state to enforce a child-support order issued by another state, and generally bars other states from modifying it except under narrow continuing-jurisdiction rules — this works alongside New Hampshire's adoption of the Uniform Interstate Family Support Act (UIFSA) to determine which state's order controls (28 U.S.C. § 1738B).

Child support and bankruptcy

If a paying parent files for bankruptcy, child support (and alimony) generally can't be eliminated. These "domestic support obligations" are non-dischargeable and are paid ahead of most other unsecured debts in the bankruptcy process (11 U.S.C. §§ 507, 523).

A note on alimony deadlines (separate from child support)

Alimony is a distinct legal issue from child support, but if it's on the table in your case, its timing rules are worth flagging now: under New Hampshire law, a request for term alimony must generally be made either before the final divorce decree becomes effective, or no later than 5 years from the effective date of the decree (RSA 458:19-a). Missing that window can foreclose an alimony claim, so confirm the deadline with your New Hampshire court if this applies to you.

What you can do in New Hampshire

1. Gather income documentation for both parents — pay stubs, tax returns, self-employment records — since the guideline calculation depends on accurate gross and net income figures.
2. Ask the court or your New Hampshire family division about the current guideline worksheet so the applicable percentage and any deductions are applied correctly to your combined net income.
3. Track your actual parenting-time percentage if you share custody, since crossing the 40% or 35% thresholds can trigger a presumption that changes the support amount.
4. If you believe special circumstances apply (extraordinary medical or education costs, a big income disparity, stepchildren, etc.), raise them with the court and be ready to document them, since deviation requires proof.
5. If it's been three years since your last order, or your circumstances have substantially changed, you can file a modification petition — but remember the change only takes effect after the other parent receives notice.
6. If support isn't being paid, contact New Hampshire's child support enforcement program about income withholding or other enforcement tools, especially if the other parent lives out of state.

This article is general information about New Hampshire law, not legal advice for your specific situation — consult a licensed New Hampshire attorney or your local family division.