How New Hampshire Calculates Child Support
New Hampshire uses the Percentage of Combined Net Income model to determine child support obligations. This page explains the guidelines, formula, and key factors.
Model Type
Percentage of Combined Net Income
New Hampshire applies a statutory percentage table to the parents' combined ANNUAL net income, interpolating linearly between the table's breakpoints. A self-support reserve protects a minimum standard of living for the paying parent before support is owed.
Sources & Verification
- Federal income tax is estimated with 2025 single-filer brackets rather than the exact DHHS-published withholding table for 'a single person who has claimed a withholding allowance for 2 people' (RSA 458-C:2, VI), which was not accessible (dhhs.nh.gov blocked automated fetches). Results may differ from the official worksheet.
- Does not collect the RSA 458-C:2, I(b)-(d) deductions for self-employment tax, mandatory retirement contributions, or state income tax paid.
Income Basis & Definitions
combined net income (annual table, both parents)
Selects percentage applied to combined net income.
Source: RSA 458-C:3: Percentage of combined net income by number of childrenParent A adjusted gross income (gross minus specified deductions).
Source: RSA 458-C:2: Adjusted gross income definitionParenting Time Handling
Calculator adjusts for parenting schedule.
Source: RSA 458-C:5: Parenting schedule adjustmentPercentage of residential responsibility with each parent.
Source: Parenting time inputDeductions & Adjustments
Preexisting support obligations reduce available income.
Source: RSA 458-C:2: Other support obligationsAdd-Ons & Allocation
Health insurance and uninsured medical allocation.
Source: RSA 458-C:3-a: Medical supportCaps, Minimums & Deviations
Guidelines apply to combined net income up to statutory cap; above-cap at discretion.
Source: Income capSpecial circumstances deviation per RSA 458-C:5.
Source: RSA 458-C:5: Special circumstances