Divorce Deep DiveIntermediate7 min read

Alimony and child support: the financial picture

How courts calculate them, how taxes treat them differently, and when the numbers can change.

Alimony (spousal support) and child support serve different purposes, follow different rules, and have completely different tax treatment. Confusing the two — or failing to plan for either — is one of the most common financial mistakes in divorce. Both the paying and receiving spouse need to understand these mechanics to build a realistic post-divorce budget.

Alimony basics

Alimony exists to prevent one spouse from falling off a financial cliff after divorce, particularly when one spouse earned significantly more or one stayed home to raise children. The amount and duration vary wildly by state. Some states use formulas (New York: 40% of the higher earner's income minus 50% of the lower earner's income, capped at certain thresholds). Others leave it to judicial discretion. Duration often tracks the length of the marriage: a 5-year marriage might yield 2–3 years of alimony, while a 20-year marriage could result in 10+ years or even permanent support.

The tax picture changed in 2019

Post-2018 alimony is not tax-deductible

For divorce agreements finalized after December 31, 2018, alimony is no longer deductible by the payer and no longer taxable income for the recipient. This was a major change from the Tax Cuts and Jobs Act. If you're paying $3,000/month in alimony, it costs you the full $3,000 — not the after-deduction amount. If you're receiving it, you keep the full $3,000 tax-free. This shifts the effective cost significantly toward the higher earner.

Child support: less negotiable

Child support is calculated by state guidelines based on both parents' incomes, the number of children, and the custody split. There is much less room to negotiate compared to alimony. Child support is never tax-deductible for the payer and never taxable for the recipient — that hasn't changed. It typically continues until the child turns 18 (or 19–21 in some states, or through college if the agreement specifies). Failure to pay child support has serious consequences: wage garnishment, license suspension, and even jail time.

When the numbers change

Job loss or significant income change: either party can petition the court for a modification. But you must file — the obligation doesn't automatically adjust.
Remarriage: alimony typically ends if the recipient remarries. Child support does not change based on remarriage.
Cohabitation: many states allow alimony reduction if the recipient moves in with a new partner, but proving cohabitation can be difficult.
Children aging out: child support recalculates when one child reaches the age limit, but again, you often need to file for the change.
Cost of living: some agreements include annual COLA adjustments. If yours doesn't, inflation erodes the real value over time.

If you're the higher earner negotiating a divorce, run the total cost of alimony versus a larger upfront asset split. Paying $4,000/month in alimony for 7 years totals $336,000 — plus the risk of modification disputes. Giving up $300,000 more in assets now might be cheaper and cleaner. Your attorney and financial advisor should model both scenarios.

Put this into practice

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