There’s no national child-support formula. Your state follows one of three models — Income Shares, Percentage of Income, or the Melson Formula — and your number turns on both parents’ income, the number of children, and parenting time.

• 41states use Income Shares (both parents’ income counts)
• 6states use Percentage of Income (only the payer’s income)
• 3states use the Melson Formula (each parent’s needs come first)

Washington, D.C. uses its own hybrid model. Source: National Conference of State Legislatures (NCSL), 2026.

Below, we walk through a real worked example, the factors that quietly raise or lower your number, and the traps most parents don’t see coming.

How Child Support Works (and Who Pays Whom)

Both parents owe a legal duty to support their child financially, whether or not they were ever married and whether or not they get along. Child support is simply the mechanism that carries that duty out when the parents live apart: money moves so that the child’s day-to-day costs are covered in both homes.

In practice, the parent the child lives with most of the time — the custodial or primary parent — usually receives support, and the other parent — the non-custodial parent — usually pays it. That’s about living arrangements and the numbers, not about who is a “better” parent. Support is framed in law as the child’s right, which is why parents generally can’t just agree to waive it; a court reviews any agreement and protects the child’s interest.

The guidelines are the formulas each state’s courts use to turn income and parenting time into a dollar figure, so that families in similar situations get similar numbers. Child support is closely tied to the broader cost and process of divorce, but it’s decided on its own track, and custody arrangements feed directly into it, as we’ll see next.

The 3 Child Support Models (Find Yours)

The single biggest factor in how your number is calculated is which model your state uses. According to the National Conference of State Legislatures, every state follows one of three approaches (with Washington, D.C. running a hybrid). Find your state in the table above, then read the matching card.

• Used by 41 states + Guam & U.S. Virgin Islands Income Shares

  Whose income counts: both parents’. The idea is that the child should get the same share of combined parental income they’d have received if the family lived together. The court combines both incomes, looks up a “basic obligation” on the state’s schedule (based on combined income and the number of children), then splits it in proportion to each parent’s share of that income.

• Used by 6 states Percentage of Income

  Whose income counts: only the paying parent’s. A set percentage is applied to the non-custodial parent’s income, rising with the number of children — Alaska, Mississippi, Nevada, North Dakota, Texas, and Wisconsin. Some use a flat percentage; Texas and North Dakota use a percentage that varies with income.

• Used by 3 states Melson Formula

  Whose income counts: both parents’, needs-first. Used only in Delaware, Hawaii, and Montana, it’s the most complex model. It first sets aside enough income for each parent’s own basic needs, then covers the child’s primary needs, then adds a share of any leftover income so the child benefits from a parent’s higher standard of living.

A Real Example: How the Math Actually Works

The clearest way to understand your state’s model is to watch it run once. Here’s a simplified income-shares example — the model used in most states. The numbers are illustrative; your real “basic obligation” comes straight from your state’s own schedule.

1. Start with each parent’s gross monthly income. Parent A: $5,000. Parent B: $10,000.
2. Add them for the combined income the child would have shared in an intact home: $15,000/month.
3. Work out each parent’s share of that combined income. Parent A = 1/3 (33%). Parent B = 2/3 (67%).
4. Look up the state’s basic obligation for $15,000 combined and, say, one child. For this example, assume the schedule gives $1,500/month.
5. The higher-earning, non-custodial parent (B) is responsible for their income share of that obligation: 2/3 of $1,500 ≈ $1,000/month paid to Parent A — before adjusting for overnights and add-ons.

From there, the court adjusts: parenting time (more overnights with the payer generally lowers the transfer), plus the child’s health-insurance premium and work-related childcare, which are added to the base and split by the same income shares.

A percentage-of-income state skips the “combine incomes” step entirely — it applies a fixed percentage to the paying parent’s income only. In Texas, for example, the guideline is roughly 20% of net resources for one child, rising about 5 points per additional child, subject to a cap on countable income. And this is exactly what an online child support calculator does behind the scenes: it plugs your real income, kids, and overnights into your state’s schedule. Use your state’s official calculator for a number you can rely on.

What Changes Your Child Support Amount

Two families with identical incomes can end up with very different numbers because of the factors below. These are where most negotiation — and most confusion — actually happens.

• Parenting time & overnights (including 50/50)

  More overnights with the paying parent generally reduces the transfer. Many states apply a shared-parenting adjustment once you cross a threshold — around 146 overnights in Illinois, or roughly 20%+ of overnights (about 73+ nights) triggering Florida’s gross-up. Even in a 50/50 split, the higher earner usually still pays something: equal time rarely means zero support when incomes differ.

• Health insurance & childcare

  The child’s share of health-insurance premiums and work-related childcare (daycare so a parent can work) are typically added to the base obligation and split proportionally by income. These add-ons can move the number meaningfully.

• Other children & support orders

  Supporting other children — or a pre-existing support order, plus alimony you pay or receive — adjusts the income the formula runs on. Extraordinary medical or special-education costs can be added on top.

• What counts as income

  Most states use gross income (some use net) and count far more than base salary: overtime, bonuses, commissions, tips, and self-employment income generally count when they’re regular and recurring. A true one-time windfall may be treated differently, but you can’t simply leave predictable extra pay off the table.

3 Things That Can Change the Number (That People Miss)

These come up constantly and catch parents off guard. Each one can change your obligation — or the trouble you’re in — more than the base formula does.

• 1. You can’t lower support by earning less on purpose

  Quitting a job, going part-time, or taking an under-the-table role to shrink your number is known as “voluntary impoverishment,” and courts don’t accept it. A judge can impute income — assign you an earning capacity based on your work history, skills, and local job market — and calculate support on what you could earn, not what you chose to report.

• 2. Above a high-income cap, the formula stops

  Guideline schedules only go so high. Above a combined-income threshold (Maryland’s is around $30,000/month, for example), the formula runs out and the court switches to the child’s actual needs and accustomed standard of living. Very high earners aren’t strictly bound to a formula figure, in either direction.

• 3. Don’t just stop paying — file to modify

  A job loss or income drop doesn’t change your order automatically. You have to request a modification, which usually requires a “material change in circumstances” — often a swing of about 15–20%. Until a judge signs off, the old amount keeps accruing, and unpaid support becomes arrears (frequently with interest) that generally can’t be erased after the fact. The fix is filing, not falling behind.

How Long Does Child Support Last?

As a general rule, support ends at the age of majority — 18 — or high-school graduation, whichever is later. But the exact age varies by state. Some run support to 19, a few (New York, Mississippi, and Washington, D.C.) to 21, several allow a court to order college or post-secondary support, and support for an adult child who can’t become self-supporting because of a disability can continue indefinitely. The termination column in the state table above shows the typical endpoint where you live.

One thing surprises many payers: support rarely stops on its own the day a child turns 18. In most places the order has to terminate by its own terms or a parent has to file to end it and stop the wage withholding. And if your order was issued in another state, that state’s end-age usually controls even after everyone moves away, under the interstate rules that govern support. Check your order’s exact language before assuming anything stops automatically.

What Happens If You Don’t Pay

Child support is a court order, and states have strong, mostly automatic tools to collect it. This is meant as plain information, not a scare tactic — knowing the tools is how you avoid them.

• 50–65%cap on wage garnishment (disposable earnings)
• $2,500arrears that trigger passport denial
• SSIneeds-based, protected from garnishment

The most common tool is income withholding (wage garnishment). Under federal law, that’s capped at 50% of disposable earnings if you support another spouse or child, 60% if you don’t, plus another 5% if you’re 12 or more weeks behind — up to 65%. Other tools include tax-refund interception, suspension of a driver’s, professional, or recreational license, passport denial once arrears pass $2,500, bank liens, and — for willful refusal to pay when someone can afford it — contempt of court and possible jail. Jail is generally a last resort aimed at willful non-payment, not at parents who genuinely can’t pay.

As for disability and veterans’ benefits: SSDI (which is based on your work record) and VA disability can generally be tapped for child support — though VA disability is protected unless it replaces waived military retirement pay. SSI, because it’s needs-based public assistance, is protected and can’t be garnished for support. If your child receives dependent or “derivative” benefits on your SSDI record, those payments may offset part of your obligation.

Is Child Support Taxable?

No — and this one is refreshingly simple. Child support is not taxable income to the parent who receives it and not tax-deductible for the parent who pays it. It has no effect on either parent’s federal return, and you can’t “claim child support” on your taxes in either direction.

That’s different from some older alimony arrangements: under agreements finalized before 2019, alimony could be deductible to the payer and taxable to the recipient — but child support was never treated that way. A separate question is who claims the child as a dependent and gets the Child Tax Credit; that’s decided by custody rules and your divorce agreement, not by who pays support. Because support isn’t deductible, it’s also worth knowing which deductions you can actually claim.

Alimony vs. Child Support (Quick Difference)

They’re often confused, but they’re separate orders that can exist at the same time. Child support is for the child’s needs, set by a state formula, not taxable, and it ends when the child is grown. Alimony (spousal support) is for a former spouse, decided by different factors like the length of the marriage and the earning gap, can be temporary or long-term, and — under older, pre-2019 agreements — may be taxable and deductible. If you’re weighing how support obligations get set up in the first place, a prenuptial agreement can address spousal support but generally can’t waive child support, since that belongs to the child.

Frequently Asked Questions

How is child support calculated?

Your state applies one of three formulas: Income Shares (combines both parents’ incomes and splits a schedule amount by income share), Percentage of Income (a set percentage of the paying parent’s income), or the Melson Formula (reserves each parent’s basic needs first). Your number then adjusts for parenting time, health insurance, and childcare.

How much is child support for one child?

It depends entirely on your state and both incomes, so there’s no single figure. As a rough illustration, income-shares states often direct somewhere around 17–20% of combined income toward one child, while a percentage-of-income state like Texas applies about 20% of the payer’s net resources. Treat these as ballparks and use your state’s calculator for a real number.

Does child support count as income (for taxes or otherwise)?

Not for federal taxes. Child support is not taxable to the parent who receives it and not deductible for the parent who pays it. (Separately, some benefit and aid programs may look at support received when assessing a household — but the IRS does not treat it as taxable income.)

Do overtime and bonuses count toward child support?

Generally yes, when they’re regular and recurring. Most states count overtime, bonuses, commissions, tips, and self-employment income as part of gross income. A genuine one-time windfall may be handled differently, but predictable extra pay usually counts.

How does 50/50 custody affect child support?

Equal parenting time usually lowers the amount but rarely eliminates it. Most states apply a shared-parenting adjustment once overnights cross a threshold, yet when incomes differ, the higher earner typically still pays something so the child’s standard of living is similar in both homes.

Can I be forced to pay if I deliberately earn less (imputed income)?

Yes. If a court finds you’re voluntarily unemployed or underemployed to reduce support, it can impute income — calculate your obligation on what you’re capable of earning based on your history and the job market — rather than on your reduced actual earnings.

How long do I have to pay child support?

Usually until the child turns 18 or graduates high school, whichever is later, though several states run to 19 and a few to 21. Support can extend for college in some states and can continue indefinitely for a disabled adult child. Check your state and your specific order.

Can child support be modified?

Yes. You can request a modification after a material change in circumstances — a job loss, a significant income change, or a change in custody — often shown by a swing of roughly 15–20%. The change isn’t automatic; you have to file, and the old amount stands until a judge changes it.

What happens if I don’t pay — can I go to jail?

Enforcement usually starts with wage garnishment, tax-refund interception, and license or passport holds. Jail is possible but generally reserved for willful refusal to pay by someone who can afford it — not for genuine inability to pay. If you can’t pay, file to modify rather than stopping.

Can child support be taken from disability or VA benefits?

SSDI and, in most cases, VA disability can be used to pay child support (VA benefits are protected unless they replace waived military retirement pay). SSI, which is needs-based, is protected and cannot be garnished for support.

Is child support taxable or tax-deductible?

Neither. It has no effect on either parent’s federal return: the recipient doesn’t report it as income, and the payer can’t deduct it. You cannot claim child support on your taxes.

What’s the difference between child support and alimony?

Child support is for the child, formula-based, and not taxable; alimony is for a former spouse, based on different factors, and may be taxable or deductible under older agreements. They can both be ordered in the same case and are calculated separately.

This article is for general educational purposes only and is not legal or tax advice. Child support guidelines, percentages, termination ages, and procedures vary by state and change over time, and every case turns on its own facts. Use your state’s official child-support calculator and consult a licensed family-law attorney or your state child-support agency for your specific situation.

Sources and further reading: the National Conference of State Legislatures guideline-model breakdown; the federal Office of Child Support Services for program and enforcement basics; a state self-help library such as the Maryland People’s Law Library for income-shares mechanics, imputed income, and the high-income cap; and your own state’s official child-support calculator and agency for the numbers that apply to you.