Calculate Illinois spousal maintenance using the 750 ILCS 5/504 formula — 33.3% of payor net minus 25% of payee net, with a 40% combined income cap and tiered duration table.
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IL Formula (750 ILCS 5/504): 33.3% × Payor Net − 25% × Payee Net = $22,470/yr 40% Combined Net Cap: $18,000/yr Result: $18,000/yr (cap applied)
Illinois Maintenance Amount
$1,500/mo
Annual Amount$18,000/yr
33.3% Payor Net$29,970
25% Payee Net$7,500
40% Cap AppliedYes
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IL Maintenance — 750 ILCS 5/504
$2,767/mo
Duration5.8 yrs
Duration %48%
Est. total$191,232
Formula Breakdown
Step 1: 33% × payor gross = $46,200
Step 2: 25% × payee gross = $13,000
Step 3: Difference = $33,200/yr
Step 4: 40% of combined net cap = $76,800/yr
Result: $33,200/yr = $2,767/mo
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Base Formula Amount
$3,804/mo
750 ILCS 5/504
Adjusted Amount
$3,804/mo
7.8 yrs
750 ILCS 5/504(a) Factor Analysis
Income of each party (§504(a)(1))
77
Needs of each party (§504(a)(2))
69
Present/future earning capacity (§504(a)(3))
56
Duration of marriage (§504(a)(4))
70
Standard of living (§504(a)(7))
83
Contribution to marriage (§504(a)(8))
65
Non-marital property (§504(a)(9))
0
Deviation Factors
Imputed income (voluntary underemployment)
Increases effective payee income for formula
decrease
Non-marital property of payee
Large payee assets reduce demonstrated need
decrease
Disability or illness
Medical limitations extend duration or increase amount
increase
Custodial caregiver responsibilities
Limits earning ability during custody years
increase
Premarital standard of living
Court may limit award to pre-marriage baseline
decrease
Career/educational contributions
Sacrifice for payor's career supports larger award
increase
How Illinois Maintenance Is Calculated
Illinois has one of the most transparent spousal maintenance formulas in the United States. Under 750 ILCS 5/504, the maintenance amount is calculated using a straightforward net-income formula, and the duration is determined by a tiered percentage table linked to marriage length. Unlike many states, Illinois gives parties and attorneys a clear, predictable starting point.
The formula applies when the combined gross income of both spouses does not exceed $500,000 per year. Above that threshold, the court has broader discretion.
Illinois Maintenance Formula
Amount Formula (750 ILCS 5/504):
Step 1: 33.3% × Payor's Net Annual Income
Step 2: 25% × Payee's Net Annual Income
Step 3: Amount = Step 1 − Step 2
Cap Rule: Amount cannot cause payee's income to exceed
40% of the parties' combined net annual income
Effective cap: (Combined Net × 40%) − Payee Net
Duration Table (% of marriage length):
<5 yrs: 20% | 13–14 yrs: 56%
5–6 yrs: 24% | 14–15 yrs: 60%
6–7 yrs: 28% | 15–16 yrs: 64%
7–8 yrs: 32% | 16–17 yrs: 68%
8–9 yrs: 36% | 17–18 yrs: 72%
9–10 yrs: 40% | 18–19 yrs: 76%
10–11 yrs: 44% | 19–20 yrs: 80%
11–12 yrs: 48% | 20+ yrs: Permanent
12–13 yrs: 52%
Note: Illinois uses net income (after federal/state taxes, Social Security, Medicare) for the formula — not gross income. This is an important distinction from states like New York that use gross income.
Example: 10-Year Illinois Marriage
Maintenance Calculation
Payor net annual income$90,000
Payee net annual income$30,000
33.3% × $90,000$29,970/yr
25% × $30,000$7,500/yr
Formula result$22,470/yr = $1,873/mo
40% cap check: (40% × $120k) − $30k$18,000/yr
Final amount (cap applies)$18,000/yr = $1,500/mo
Duration (10 yrs × 44%)4.4 years
Total maintenance$79,200
In this example, the 40% combined income cap reduces the maintenance from $22,470 to $18,000/year. Without the cap, the payee's income ($30,000 + $22,470 = $52,470) would exceed 40% of combined net ($48,000).
Frequently Asked Questions
Illinois uses net income — income after federal and state income taxes, Social Security, and Medicare contributions. This is a key distinction from states like New York and Texas that use gross income. Using net income generally produces a lower alimony figure, and it avoids the double-taxation issue common with gross income formulas.
The 40% cap prevents the maintenance formula from putting the payee in a better financial position than the payor. Specifically, the maintenance cannot cause the payee's total net income (their own income plus maintenance) to exceed 40% of the parties' combined net income. If the formula result would breach this cap, the amount is reduced to the cap limit.
Under Illinois law, marriages of 20 or more years may result in an order of permanent maintenance. "Permanent" means the court may either order maintenance for an indefinite period or for a period equal to the length of the marriage — the statute gives the court discretion to choose between these two options based on the specific circumstances.
The statutory formula in 750 ILCS 5/504 applies when the parties' combined gross income does not exceed $500,000 per year. If the combined gross income exceeds $500,000, the court uses its discretion to award maintenance based on the §504(a) factors rather than the formula. The formula remains a useful reference point even for higher-income cases.
Yes. Illinois maintenance can be modified if there is a substantial change in circumstances. Either party can petition for modification. The court will determine whether the change is substantial enough and recalculate based on current incomes. Automatic cost-of-living adjustments can be built into the original order. Maintenance terminates upon the death of either party or the remarriage of the recipient.