New Hampshire Child Support Guidelines: How Support Is Calculated

New Hampshire uses a Income shares framework under N.H. Rev. Stat. Ann. § 458-C:1 et seq.. This guide explains how courts calculate support from net income, when judges may deviate, how modification works, and how leading New Hampshire opinions apply the statute. Pair this article with the CaseDiver search rail to pull additional New Hampshire family-law decisions.

Primary keywords: New Hampshire child support guidelines, RSA 458-C, New Hampshire child support calculator, modify New Hampshire child support

Key takeaways

• New Hampshire follows the Income shares model for presumptive child support.
• Income is generally measured using net income, then allocated under N.H. Rev. Stat. Ann. § 458-C:1 et seq..
• Guideline amounts are presumptive, not automatic — courts may deviate when the facts justify it.
• Support generally ends at 18, or upon high-school graduation if later, not past 19 in ordinary cases.
• Either parent can seek modification when substantial change in circumstances; a 20% difference between existing and recalculated support is a common threshold..
• Read the companion guide: New Hampshire alimony / alimony.

Statutory framework and guideline model

New Hampshire's child support system is built around N.H. Rev. Stat. Ann. § 458-C:1 et seq.. Under the income shares, New Hampshire guidelines use net income figures and percentage shares based on combined income to set a total support obligation, then allocate between parents. Adjustments exist for parenting time, medical support, and childcare.

Federal law requires every state to maintain presumptive guidelines and to review them at least every four years (42 U.S.C. § 667). Confirm the latest New Hampshire schedule or worksheet before relying on any online calculator.

How child support is calculated in New Hampshire

1. Identify each parent's guideline income using net income as defined in N.H. Rev. Stat. Ann. § 458-C:1 et seq. and the accompanying worksheets or administrative rules.
2. Apply the income shares — whether that means a combined-income schedule, an obligor percentage table, or a Melson-style self-support reserve plus primary obligation.
3. Allocate add-ons such as health insurance premiums, unreimbursed medical expenses, and work-related child care according to New Hampshire practice.
4. Consider parenting time adjustments where the guidelines or case law authorize a credit or shared-custody formula.
5. Test for deviation if a strict guideline result would be unjust or inappropriate on the record.

Online calculators can illustrate ranges, but only the controlling statute, guidelines, and court findings produce an enforceable order.

Deviation from the guidelines

Statutory special circumstances allow deviation when the guideline result is unjust or inappropriate.

When a court departs from the presumptive amount, New Hampshire practice generally requires findings that explain why the guideline figure is unjust or inappropriate and what amount better serves the child's needs. Those findings matter on appeal and in later modification proceedings.

Modification of child support

Substantial change in circumstances; a 20% difference between existing and recalculated support is a common threshold.

A parent seeking a change typically must show that circumstances after the prior order make the existing award inequitable. Common triggers include job loss, substantial income changes, a new parenting-time schedule, emancipation of a child, or extraordinary medical needs. Retroactivity and temporary relief rules are statute-specific — check N.H. Rev. Stat. Ann. § 458-C:1 et seq. and local family-division procedures.

Enforcement in New Hampshire

Division of Child Support Services enforces with withholding, intercepts, and contempt.

Interstate cases often implicate UIFSA. Income withholding, contempt, license suspension, and tax-refund intercept remain core tools nationwide, but the New Hampshire child support agency and clerk of court procedures control day-to-day collection.

When child support ends

In New Hampshire, Support generally ends at 18, or upon high-school graduation if later, not past 19 in ordinary cases. Orders may extend for disability, secondary education, or other statutory grounds where the statute allows. Always read the judgment language — agreed orders sometimes set a different end date or require a notice of emancipation.

Case law: how New Hampshire courts apply the guidelines

The opinions below are in the LawDiver corpus. Each block quote is taken from the opinion text so you can jump from this guide into the full decision.

In the Matter of Susan L. Forcier and Todd S. Mueller

In the Matter of Susan L. Forcier and Todd S. Mueller, 152 N.H. 463 (2005)

…Todd S. Mueller, to deduct $626 each month out of his total child support obligation and place *464this amount into a college trust fund for the benefit of the parties’ children. We vacate and remand. The record supports the following facts. After the parties obtained a divorce in September 1991, the respondent was awarded primary physical custody and the petitioner received re…

Courts and practitioners still cite this opinion when litigating new hampshire child support issues. Open the full text on LawDiver to read the holding in context.

In the Matter of Linda A. Plaisted and Grahame J. Plaisted

In the Matter of Linda A. Plaisted and Grahame J. Plaisted, 149 N.H. 522 (2003)

…nis, J. The respondent, Grahame J. Plaisted, appeals from a child support order of the Superior Court (Hampsey, J.) requiring him to pay weekly support of $180 while he is unemployed. We reverse in part, vacate in part and remand. *523The record contains the following relevant facts. The parties were divorced in March 1998. The respondent was initially ordered to pay $270 per w…

Courts and practitioners still cite this opinion when litigating new hampshire child support issues. Open the full text on LawDiver to read the holding in context.

In the Matter of Toni E. Jerome and Raymond W. Jerome

In the Matter of Toni E. Jerome and Raymond W. Jerome, 150 N.H. 626 (2004)

…of the Superior Court (Burling, J.) modifying the parties’ child support obligations to include her personal injury annuity as income for child support purposes. We affirm. The record supports, or the parties agreed to, the following facts. The petitioner and the respondent, Raymond W. Jerome, were married in 1984 and had a son in 1987. In 1985, the parties sued a security com…

Courts and practitioners still cite this opinion when litigating new hampshire child support issues. Open the full text on LawDiver to read the holding in context.

Debra Rattee v. Steven Rattee

Debra Rattee v. Steven Rattee, 146 N.H. 44 (2001)

…stipulation, pursuant to which the defendant agreed to pay child support of $1,531 per week for the two minor children. This amount was consistent with New Hampshire child support guidelines. See RSA ch. 458-C (1992 & Supp. 2000). The defendant later moved for a further temporary hearing on child support on the ground that the middle child was emancipated. In response, the pla…

Courts and practitioners still cite this opinion when litigating new hampshire child support issues. Open the full text on LawDiver to read the holding in context.

Practical checklist for New Hampshire child support matters

• Gather recent pay stubs, tax returns, and proof of health insurance / child-care costs.
• Complete the current New Hampshire worksheet or financial affidavit required by the local court.
• Document parenting-time overnights if a shared-custody adjustment may apply.
• Flag facts that could support deviation (special needs, travel costs, high income, other children).
• Search LawDiver for recent New Hampshire appellate decisions before mediation or trial.

Frequently asked questions

How is child support calculated in New Hampshire?

New Hampshire uses the income shares under N.H. Rev. Stat. Ann. § 458-C:1 et seq.. Courts start with net income, apply the guideline schedule or percentage, allocate add-ons, and may deviate with findings when the presumptive amount is unjust.

What income counts for New Hampshire child support?

Guideline income generally tracks net income as defined by N.H. Rev. Stat. Ann. § 458-C:1 et seq. and the worksheets. Wages, self-employment income, bonuses, and certain benefits are commonly included; exact deductions and exclusions are statute-specific.

Can New Hampshire courts order more or less than the guideline amount?

Yes. Guideline support is presumptive. Judges may deviate when the record shows the guideline result is unjust or inappropriate, typically with written findings explaining the departure.

How do I modify a New Hampshire child support order?

Substantial change in circumstances; a 20% difference between existing and recalculated support is a common threshold. File in the court with continuing jurisdiction (or follow UIFSA for interstate cases) and support the request with current financial evidence.

When does child support end in New Hampshire?

Support generally ends at 18, or upon high-school graduation if later, not past 19 in ordinary cases. Confirm any disability, educational, or agreed extensions in your particular order.

Where can I research New Hampshire child support case law?

Use LawDiver CaseDiver search scoped to New Hampshire, or open the opinions linked in this guide. Companion reading: New Hampshire alimony guide.

Disclaimer

This guide is general legal information about New Hampshire child support, not legal advice. Statutes, guidelines, and case law change. Confirm the current text of N.H. Rev. Stat. Ann. § 458-C:1 et seq. and consult a licensed New Hampshire family-law attorney about your facts.