Illinois Alimony Calculator

Illinois calls it spousal maintenance, and 750 ILCS 5/504(b-1)(1)(A) sets the guideline amount at 33 1/3% of the payor's net annual income minus 25% of the payee's net annual income. That result is then capped: when added to the payee's own net income, maintenance cannot push them above 40% of the couple's combined net income. The guidelines apply only when combined gross annual income is under $500,000 and the payor has no child support or maintenance obligation from a prior relationship.

The 40% rule is the statutory cap on the guideline amount. After applying the 33 1/3% minus 25% formula, the court checks whether the resulting maintenance plus the receiving spouse's own net income exceeds 40% of the parties' combined net income. If it does, maintenance is reduced so the total lands exactly at 40%. The cap binds most often when both spouses earn — it is the reason two couples with the same income gap can end up with very different awards.

Duration is the length of the marriage multiplied by a statutory factor under 750 ILCS 5/504(b-1)(1)(B). The factor starts at 0.20 for marriages under 5 years and rises by 0.04 for each additional year, reaching 0.80 at 19 years. For marriages of 20 years or more, the court orders maintenance either for a period equal to the length of the marriage or for an indefinite term.

Net income. Illinois switched to net income after the 2019 federal tax change that made maintenance neither deductible for the payor nor taxable for the recipient. Net income means gross income minus federally and state-required deductions such as income tax, Social Security and Medicare, mandatory retirement contributions, and union dues.

The statutory guidelines stop applying. Above $500,000 in combined gross annual income, or where the payor already owes child support or maintenance from a prior relationship, the court sets maintenance case by case using the factors in 750 ILCS 5/504(a) — the standard of living during the marriage, each spouse's needs and earning capacity, contributions one spouse made to the other's career, and the realistic time needed for the recipient to become self-supporting.

Not for orders entered after December 31, 2018. The Tax Cuts and Jobs Act ended the federal deduction for the paying spouse and the corresponding income inclusion for the recipient. Orders finalized before that date generally keep the old treatment unless they are modified and the parties expressly adopt the new rules.

Yes. Maintenance can be modified on a substantial change in circumstances under 750 ILCS 5/510. It terminates automatically on the death of either party, the recipient's remarriage, or the recipient cohabiting with another person on a continuing conjugal basis. Courts can also award fixed-term maintenance that is explicitly non-modifiable.

It applies the statutory guideline formula and duration table, which is what an Illinois court starts from in a typical case. It cannot account for deviations a judge may order, prior-relationship support obligations, income above the $500,000 ceiling, disputed income figures, or the many discretionary factors in 750 ILCS 5/504(a). Treat the result as a starting point and confirm it with an Illinois family law attorney.