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Illinois Alimony Calculator & Spousal Support Guidelines (2026)

Calculate Illinois spousal support with the statutory formula under 750 ILCS 5/504 — amount, duration rules, and a worked example.

Estimate Spousal Support

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Illinois Alimony Rules at a Glance

How amount is set Statutory formula
Formula / practice 33.3% of the payor’s net income minus 25% of the recipient’s net income; the recipient’s total (income + maintenance) may not exceed 40% of combined net income. Duration = marriage length x a statutory multiplier.
Statute 750 ILCS 5/504
Parameters verified 2026-07

Worked Example: $8,000 vs $3,000 Income, 12-Year Marriage

  1. Higher-earning spouse: $8,000/mo - lower-earning spouse: $3,000/mo - 12-year marriage, no concurrent child support.
  2. 33.3% x $8,000 = $2,666 minus 25% x $3,000 = $750 gives $1,916.
  3. 40% combined cap: 0.40 x $11,000 - $3,000 = $1,400 - the cap binds, so the guideline award is $1,400 per month.
  4. Duration: 12-year marriage x 0.52 multiplier = about 6.2 years.

Result: $1,400 per month - typical duration: 6.2 years (12 yr marriage x 0.52)

Illinois Alimony FAQ

How is alimony calculated in Illinois?

Illinois uses a statutory guideline under 750 ILCS 5/504. 33.3% of the payor’s net income minus 25% of the recipient’s net income; the recipient’s total (income + maintenance) may not exceed 40% of combined net income. Duration = marriage length x a statutory multiplier.

How long does alimony last in Illinois?

Marriage length x a statutory multiplier (0.20 for under 5 years, rising 0.04 per year, to indefinite or marriage-length at 20+ years).

When does alimony end in Illinois?

Alimony typically ends on the recipient’s remarriage or either party’s death, and can be modified or terminated on the recipient’s cohabitation or a substantial change in circumstances, per 750 ILCS 5/504 and case law. Agreements can make support non-modifiable by contract.

Is alimony taxable in Illinois?

For divorces finalized after 2018, alimony is not deductible by the payor and not taxable to the recipient under federal law. State income tax treatment can differ - check current state rules.

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About This Estimate

Estimate only — not legal advice. Based on Illinois law (750 ILCS 5/504), last verified 2026-07. Courts may deviate. Consult a family law attorney for your situation.