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Illinois Alimony Calculator (2026 Maintenance Formula)

Illinois is one of the few states where alimony — legally called maintenance — follows a precise statutory formula rather than a judge's open-ended discretion. Since the 2019 amendments to Section 504 of the Illinois Marriage and Dissolution of Marriage Act, guideline maintenance is calculated from both spouses' net incomes, and the duration of payments is a fixed multiplier of the length of the marriage. This calculator applies that exact formula so you can see a realistic starting point before you talk to an attorney.

Reviewed 2026-08-27 · Estimates only — not legal or financial advice. · Ver esta página en español

Income after taxes. Illinois' guideline uses net, not gross.
Income after taxes.
From the date of marriage to the date the divorce case was filed.
The law behind this calculator: Illinois Marriage and Dissolution of Marriage Act, Section 504 — 750 ILCS 5/504(b-1).

How Illinois calculates it

  • The guideline amount is 33⅓% of the paying spouse's annual net income minus 25% of the receiving spouse's annual net income.
  • The result is capped: the recipient's total income (their own net income plus maintenance) cannot exceed 40% of the couple's combined net income.
  • The guideline applies when the couple's combined gross annual income is under $500,000; above that, the court sets maintenance case by case.
  • Duration is the length of the marriage multiplied by a statutory factor that rises from 0.20 (marriages under 5 years) to 0.80 (19–20 years); at 20 years or more the court may order maintenance for the full length of the marriage or indefinitely.

Worked example

A couple divorcing after 12 years: the payer nets $90,000 a year, the recipient nets $35,000. Guideline maintenance is 33⅓% × $90,000 − 25% × $35,000 = $30,000 − $8,750 = $21,250/year (about $1,770/month). The cap check: $35,000 + $21,250 = $56,250, which exceeds 40% of the $125,000 combined net ($50,000) — so the award is reduced to $15,000/year ($1,250/month). Duration: 12 years × 0.52 = about 75 months.

Frequently asked questions

Is the Illinois maintenance formula mandatory?

Courts must either apply the guideline or explain on the record why they deviated from it. In practice, most Illinois maintenance awards under the $500,000 combined-income threshold follow the formula, which is why a calculator gives a useful estimate here.

Is alimony taxable in Illinois?

For divorces finalized after 2018, maintenance is not deductible by the payer and not taxable income to the recipient under federal law. That is exactly why the statute switched to a net-income formula — the tax burden already sits with the payer.

What counts as net income?

Gross income from all sources minus taxes and certain statutory deductions, following the same definition used for Illinois child support (750 ILCS 5/505). Wages, self-employment income, bonuses, and investment income all count.

Can maintenance be modified later?

Yes. Either ex-spouse can petition to modify or terminate maintenance after a substantial change in circumstances — job loss, retirement, or the recipient's remarriage or cohabitation, which terminates it automatically.

Does marital misconduct affect the amount?

No. Illinois is a no-fault state and Section 504 expressly bars courts from considering marital misconduct when setting maintenance.

Is the calculation different in Chicago, Naperville or Lake Forest?

No. 750 ILCS 5/504(b-1) applies statewide, so courts in Chicago, Naperville, Lake Forest, Springfield and every other county start from the same guideline. Local practice can differ in how judges weigh deviation factors and in typical negotiated outcomes, but the formula on this page is the one used across Illinois.

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StateTally. (2026). Illinois Alimony Calculator (2026 Maintenance Formula). Retrieved October 13, 2026, from https://statetally.com/alimony/illinois/