Child Support Calculations in New Hampshire

New Hampshire uses the Income Shares model under RSA 458-C, with significant 2025 updates to parenting-time presumptions. Whether you're navigating an uncontested or contested divorce, understanding the formula, medical support rules, and the new shared-parenting presumptions is essential.

The Income Shares Model

New Hampshire determines child support by combining both parents' net incomes, finding the total obligation from the DHHS schedule, and allocating that total in proportion to each parent's income share.

• No income cap: The top bracket percentages apply above $125,000 combined annual net income
• Self-Support Reserve: $1,695/month (130% of federal poverty guideline as of January 2025)
• Minimum Order: $50/month unless court sets lower amount
• Medical Support: 4% of each parent's gross income (presumptive)

What Counts as Income

Gross income under RSA 458-C:2 includes:

• Employment income: Wages, salary, commissions, tips, bonuses
• Self-employment: Business profits net of legitimate expenses (plus 50% SE tax deduction)
• Benefits: Social Security, pensions, unemployment, workers' compensation, veterans' benefits, disability
• Investment income: Interest, dividends, trust income, net rental income
• Alimony received: From current or prior relationships
• Gambling winnings

Exclusions from Income

• Overtime exemption: Hourly overtime beyond 40 hours/week if occasional/seasonal in industries that customarily pay overtime
• Public assistance: SSI, TANF, SNAP not counted
• Spouse's income: Not considered unless parent voluntarily reduces work

Step-by-Step Calculation

1. Determine gross income: All sources for each parent
2. Calculate Adjusted Gross Income (AGI): Subtract allowable deductions (support paid to others, 50% SE tax, mandatory retirement, state income tax, child care/medical paid by obligor)
3. Apply DHHS standard deductions: Federal withholding, FICA, Medicare to get net income
4. Look up total obligation: Use DHHS schedule based on combined net and number of children
5. Allocate by income shares: Each parent pays proportionally based on their net income percentage
6. Apply adjustments: If obligee pays child care/medical, reduce their AGI before allocation
7. Check SSR/minimum: Apply self-support reserve protections if applicable

The Guideline Schedule Percentages

The anchor percentages from RSA 458-C:3 (at $125,000+ combined annual net income):

• 1 child: 19% (ranges from 19-25.6% depending on income)
• 2 children: 26% (ranges from 26-35.5%)
• 3 children: 31% (ranges from 31-42.5%)
• 4+ children: 33.5% (ranges from 33.5-45%)

DHHS publishes interpolated amounts in $1,000 increments annually (effective April 1).

Need a Detailed Support Estimate?

For official calculations, use the NH DHHS Child Support Calculator. For a comprehensive financial picture including custody scenarios, medical support, and parenting-time adjustments:

Build my full support plan →

2025 Parenting-Time Presumptions

Effective January 1, 2025, RSA 458-C:5 includes new rebuttable presumptions based on defined terms:

• Approximately equal: Each parent has >40% of the annual schedule
• Substantially shared: Each parent has >35% of time
• Substantially similar incomes: ≤10% difference in gross monthly incomes

The 2025 Presumptions

If parents split 50/50 all eligible child care, uninsured medical, and agreed extracurriculars:

• Similar incomes + approximately equal: Rebuttable presumption of $0 support
• Similar incomes + substantially shared: Rebuttable presumption that a deviation is appropriate
• Dissimilar incomes + no shared schedule: Presumption that guideline amount is appropriate
• Dissimilar incomes + shared/equal schedule: Court decides based on best interest

Important: New Hampshire has no automatic overnight credit. All parenting-time adjustments require written deviation findings.

Medical Support (The 4% Rule)

Every support order must include a medical support obligation:

• Presumptive amount: 4% of each parent's gross income
• Coverage requirement: Court designates who provides insurance if available at reasonable cost
• Deviation authority: Court may adjust based on RSA 458-C:5 factors
• Separate from cash support: Medical support is in addition to the cash child support amount

Self-Support Reserve Protection

The SSR protects low-income obligors from destitution:

• SSR amount (2025): $1,695/month (130% of federal poverty guideline)
• If gross < SSR: Order defaults to $50/month minimum (unless court sets lower)
• If gross > SSR but payment would push below: Order reduced to difference between SSR and AGI (but not below $50)

Duration of Support

As of July 1, 2025 (RSA 461-A:14):

• Standard termination: Age 18
• High school extension: If still a full-time student at 18, continues until graduation or 2 months after age 19 (whichever is first)
• Disabled children: Support may continue after 18 for children receiving special education (no order after July 9, 2013 extends beyond age 21)
• Automatic step-downs: Court may specify new amounts that take effect on specified dates/events

Modification Standards

Under RSA 458-C:7:

• 3-year review: Either party may seek modification without showing substantial change after 3 years
• Anytime modification: May petition at any time for "substantial change in circumstances"
• Effective date: Modifications not retroactive before the date the other party receives notice
• Overpayment adjustment: Courts must order reimbursement for overpayments after notice (absent undue hardship)

Enforcement Tools

NH DHHS and the courts can enforce support through:

• Income withholding: All orders include assignment provisions
• License suspension: Driver's, professional, and sporting licenses
• Tax intercepts: Federal and state refund interception
• Passport denial: Through Federal Offset Program
• Liens and levies: On property, bank accounts, insurance settlements
• Credit bureau reporting: Delinquencies reported
• Contempt proceedings: Show cause hearings

Interest on Arrears

New Hampshire does not impose statutory interest on child support arrears. Unless a specific order applies interest, arrears typically accrue without interest charges.

Common Calculation Mistakes

• Using gross business receipts: Self-employment uses net profits minus legitimate expenses
• Including discretionary retirement: Only mandatory contributions reduce AGI
• Expecting automatic overnight credits: NH has no overnight formula—all adjustments are deviations
• Counting public assistance: SSI, TANF, SNAP are excluded from income
• Forgetting the 50% SE tax deduction: Self-employed parents get this AGI reduction
• Confusing medical support: The 4% obligation is separate from cash child support

Key Takeaways

• Income Shares model: Both parents' incomes combined, allocated proportionally
• No income cap: Top percentages apply above $125,000/year combined
• $1,695 SSR: 130% of federal poverty guideline (eff. Jan 2025)
• $50 minimum order: Unless court sets lower
• 4% medical support: Presumptive obligation for each parent
• 2025 parenting presumptions: New defined terms and rebuttable presumptions
• No automatic overnight credit: Deviations require written findings
• No interest on arrears: Arrears accrue without statutory interest
• 3-year review: Available without showing change in circumstances
• Duration: Age 18, or graduation/2 months after 19 if in high school

For more information about New Hampshire divorce processes, see our New Hampshire divorce timeline and filing checklist. For property division information, review our New Hampshire marital property guide.