How does alimony work in Illinois?

Illinois maintenance is governed by 750 ILCS 5/504 and uses a tightly defined statutory formula for most cases.

1. Threshold — Is Maintenance Appropriate? (§ 504(a))

Before applying any formula, the court determines whether maintenance is appropriate by considering 14 statutory factors including income/property, needs, present and future earning capacity, impairment from domestic duties, time needed for education, standard of living, marriage duration, age/health, all sources of income, tax consequences, contributions to the other's education/career, prenuptial agreements, and any other just factor.

2. The Income Formula — § 504(b-1)(1)(A)

For combined gross annual incomes under $500,000 with no maintenance/child-support obligations from a prior relationship:

Maintenance = (33⅓% of payor's net annual income) − (25% of payee's net annual income)

The recipient's resulting income (maintenance + own income) may not exceed 40% of combined net income.

3. Above $500,000 Combined Income

The formula does not apply. Courts set maintenance using the § 504(a) factors with broader discretion, often tracking the formula as a guidepost.

4. Duration Schedule — § 504(b-1)(1)(B)

Duration is calculated by multiplying marriage length (in years) by:

Less than 5 years: 0.20

5 to less than 6: 0.24

6: 0.28

7: 0.32

8: 0.36

9: 0.40

10: 0.44

11: 0.48

12: 0.52

13: 0.56

14: 0.60

15: 0.64

16: 0.68

17: 0.72

18: 0.76

19: 0.80

20 years or more: equal to the length of the marriage OR indefinite.

5. Modification — § 510

Modifiable on a substantial change in circumstances. Cohabitation with another person on a resident, continuing, conjugal basis automatically terminates maintenance (§ 510(c)) — Illinois is unusual in making this a bright-line termination, not just a presumption.

6. Termination

Terminates on death of either party or remarriage of the recipient.

7. Tax Treatment

Per the federal TCJA (2017), maintenance in Illinois orders entered on/after January 1, 2019 is not deductible by the payor and not taxable to the recipient.

This is legal information, not legal advice.