How New Hampshire Calculates Child Support
New Hampshire adds both parents’ adjusted gross incomes, reads the guideline amount for the number of children in the DHHS table, and has the obligor pay his or her proportional share, limited by the self-support reserve.
Step 1: Gross income
Gross income is all income from any source, earned or unearned: wages, salary, commissions, tips, annuities, Social Security, trust income, interest, dividends, net rental income, self-employment income, alimony, business profits, pensions, bonuses and benefits such as workers’ compensation, veterans’ and unemployment benefits. It excludes means-tested public assistance, and hourly overtime beyond 40 hours in a week that is occasional or seasonal in a trade that traditionally pays it (RSA 458-C:2, IV). The court may count the difference between what a parent earns and has earned if the parent is voluntarily unemployed or underemployed.
Step 2: Adjusted gross income
Subtract court-ordered or administratively ordered support actually paid to others, 50% of actual self-employment tax, mandatory (not discretionary) retirement contributions and actual state income taxes (RSA 458-C:2, I). The obligor also subtracts the child care and medical support he or she pays for the children of this order. That gives each parent’s adjusted monthly gross income (line 6).
Step 3: The guideline table
Add the two adjusted incomes (line 6, column 3) and find the $10 row in the DHHS table; for example, $2,726 falls in the $2,720 to $2,729 row. The table converts the row’s median income to net income by deducting federal tax and FICA and applies the percentage for the number of children: 25.6% for one child, 35.5% for two, 42.5% for three and 45% for four or more at $15,000 of annual net income or less, falling to 19%, 26%, 31% and 33.5% at $125,000 or more, with the percentages in between interpolated (RSA 458-C:3).
Step 4: Proportional shares
The obligee’s child care and medical support for the children are subtracted from the obligee’s adjusted income (line 9), each parent’s share is his or her line 9 income divided by the total (line 10), and the obligor’s share of the guideline amount is line 11.
A worked example
Two children; the obligor earns $5,000 a month and the obligee $3,000, with no deductions.
| Line | Amount |
|---|---|
| Gross monthly income: obligor / obligee (line 4) | $5,000 / $3,000 |
| Combined adjusted monthly gross income (line 6, column 3) | $8,000 |
| Guideline amount for two children, row $8,000 to $8,009 (line 7A) | $1,862 |
| Percentage of net income (line 7B) | 29.41% |
| Obligor’s proportional share, 62.5% (line 10) | 62.5% |
| Parental support obligation (line 11) | $1,164 |
| Income above the $1,729 reserve (line 13) | $3,271 |
| Monthly support payable | $1,164 |
With one child the guideline amount is $1,342 and the payment $839; if the obligee pays $600 of child care and the obligor $200 for the children’s insurance, the payment becomes $1,220. The New Hampshire child support calculator reproduces these.
What to gather
Pay records and tax returns for both parents, child care and insurance statements and records of other support orders.
Rounding
All child support obligations are rounded to the nearest whole dollar (RSA 458-C:3, II(d)).
Frequently asked questions
What is the New Hampshire Child Support Guideline Table?
A DHHS table of guideline amounts in $10 rows of combined adjusted monthly gross income for one, two, three and four or more children.
How does New Hampshire treat self-employment income?
Self-employment income is gross income, and 50% of the self-employment tax actually paid is deducted.
Does New Hampshire count a new spouse’s income?
No, unless the parent resigns, refuses employment or is voluntarily unemployed or underemployed.
Is the New Hampshire worksheet required?
Yes. The party seeking an order must file a completed DHHS worksheet at every hearing on child support.
How is the New Hampshire table percentage set?
RSA 458-C:3 sets percentages at income levels and DHHS interpolates between them.
Official sources
- RSA chapter 458-C: Child Support Guidelines
- New Hampshire Child Support Guidelines booklet and Guideline Calculation Table (effective April 1, 2025)
- DHHS Child Support Guidelines Worksheet (DCSS 650)
A local family law attorney can review your situation — many offer a free consultation.
This is general information, not legal advice. It is based on the cited New Hampshire statutes, rules and court opinions, and every case turns on its own facts. Confirm how the law applies to your situation with a licensed New Hampshire attorney.