Does Illinois use gross or net income for maintenance?

Illinois uses net income — after federal and state income taxes, Social Security, and Medicare. This is distinct from states like New York that use gross income and generally produces a lower alimony figure.

What is the 40% cap in Illinois maintenance?

The 40% cap prevents maintenance from putting the payee in a better financial position than the payor. Maintenance cannot cause the payee's total net income to exceed 40% of parties' combined net income.

When does Illinois maintenance become permanent?

Marriages of 20+ years may result in permanent maintenance in Illinois. The court may order maintenance for an indefinite period or for a period equal to the marriage length — it has discretion to choose.

Does the $500,000 income limit affect my calculation?

The statutory formula applies when combined gross income does not exceed $500,000/year. Above that threshold, the court uses discretion based on §504(a) factors rather than the formula.

Can Illinois maintenance be modified?

Yes. Either party can petition for modification upon a substantial change in circumstances. Maintenance terminates on death of either party or remarriage of the recipient. COLA adjustments can be built into the original order.

Illinois Alimony Calculator

Estimate IL spousal maintenance per 750 ILCS 5/504: 33.3% payor net − 25% payee net, capped at 40% of combined net. Full per-year duration table. Non-presumptive above $500K combined gross.

Updated April 2026 750 ILCS 5/504(b-1)(1)(A) Private — runs in your browser

Payor Net Annual Income(after tax)

Payee Net Annual Income(after tax)

Marriage Length

years

IL Formula (750 ILCS 5/504(b-1)(1)(A)):
Base: 33.3% × Payor Net − 25% × Payee Net = $22,470/yr
40% Combined Net Cap: maintenance ≤ $18,000/yr (so that maintenance + payee income ≤ 40% of combined)
Result: $18,000/yr (40% cap binds)

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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Advanced Calculator

750 ILCS formula visualization, duration tier chart, and $500K combined income cap analysis.

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Payor Annual Income

Payee Annual Income

Marriage Length

yrs

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

Professional Simulator

Full deviation factors, imputed income modeling, non-marital property impact, and 20-year projections.

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Payor Annual Income

Payee Annual Income

Marriage Length

yrs

Payor Net Assets

Payee Net Assets

Imputed Income (payee)

Payee Non-Marital Property

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))

Needs of each party (§504(a)(2))

Present/future earning capacity (§504(a)(3))

Duration of marriage (§504(a)(4))

Standard of living (§504(a)(7))

Contribution to marriage (§504(a)(8))

Non-marital property (§504(a)(9))

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 in 2026

Illinois has one of the most transparent spousal maintenance formulas in the United States. Under 750 ILCS 5/504, the amount is calculated using a straightforward net-income formula, and the duration is determined by a per-year multiplier table tied to marriage length. The formula is presumptive when combined gross income is $500,000 or less — above that threshold, courts have full discretion.

Illinois Maintenance Formula

Amount (750 ILCS 5/504(b-1)(1)(A)):
Base = (33.33% × Payor Net) − (25% × Payee Net)
Statutory cap: Base + Payee Net cannot exceed 40% of Combined Net Income
Final Amount = min(Base, 0.40 × Combined − Payee Net)

Duration (§504(b-1)(1)(B)) — per-year multiplier:
Less than 5 yr: 0.20 | 5-5.9: 0.24 | 6-6.9: 0.28 | 7-7.9: 0.32
8-8.9: 0.36 | 9-9.9: 0.40 | 10-10.9: 0.44 | 11-11.9: 0.48
12-12.9: 0.52 | 13-13.9: 0.56 | 14-14.9: 0.60 | 15-15.9: 0.64
16-16.9: 0.68 | 17-17.9: 0.72 | 18-18.9: 0.76 | 19-19.9: 0.80
20+ years: court may order permanent or duration equal to marriage length

What Counts as "Net Income" in Illinois

Per §504/§505(a)(3), Illinois defines net income as gross income minus:

Federal and state income taxes
Social Security and Medicare (FICA)
Mandatory retirement contributions
Union dues
Dependent and individual health/hospitalization insurance premiums
Prior obligations of support or maintenance actually paid pursuant to court order

The 40% Combined-Net Cap — The Most-Missed Provision

The statute imposes a hard ceiling: awarded maintenance plus the payee's net income cannot exceed 40% of combined net income. Many competitor calculators miss this cap. Our calculator enforces it automatically.

Example where cap binds: Payor net $120,000/yr, payee net $80,000/yr. Combined = $200,000. 40% cap = $80,000. Base formula: (0.333 × 120,000) − (0.25 × 80,000) = $20,000. Cap check: $20,000 + $80,000 = $100,000, which exceeds $80,000 cap. Maintenance reduced to $0 (since payee already earns 40% of combined).

Above $500K Combined Gross Income

When the parties' combined gross income exceeds $500,000 per year, §504(b-1) is non-presumptive. Courts exercise full discretion on both amount and duration, considering the 14 statutory factors including the parties' standard of living during marriage, earning capacity disparities, contributions to the marriage, and tax consequences. High-income maintenance cases are heavily attorney-dependent.

Worked Example — 2026

12-Year Marriage, $120K vs $40K Net

Payor earns $120,000/yr net. Payee earns $40,000/yr net. Marriage: 12 years.

Base formula: 0.333×120,000 − 0.25×40,000$29,960/yr

Combined net × 40%$64,000

40% cap − payee net$24,000/yr

Final amount (capped)$24,000/yr ($2,000/mo)

Duration multiplier (12 yr)0.52

Duration (12 × 0.52)6.24 years

Total maintenance obligation~$149,760

Official Sources & Legal References

Frequently Asked Questions

What is the 40% combined net income cap? ▼

Under §504(b-1)(1)(A), maintenance plus the payee's net income cannot exceed 40% of the parties' combined net income. This often reduces the base formula result, especially when the payee already earns a significant income. The cap protects against over-awarding maintenance in high-earning households.

When does the formula NOT apply? ▼

Above $500,000 combined gross income, the formula is non-presumptive — courts have full discretion. Courts can also deviate below $500,000 if the statutory factors under §504(a) justify it, though they must make written findings. Parties may also agree to amounts outside the formula in a marital settlement agreement.

How is child support interaction handled? ▼

Per §505(a)(3)(g-5), when maintenance is ordered, it is deducted from the payor's net income and added to the payee's net income before the child support calculation. This prevents double-counting and ensures child support reflects post-maintenance household economics. Always run maintenance before child support in Illinois.

What happens after a 20+ year marriage? ▼

For marriages of 20 years or longer, the court may order permanent maintenance OR maintenance for a duration equal to the length of the marriage. This is judicial discretion — not a formula. Factors include age, health, income disparity, and whether the lower-earning spouse can realistically become self-supporting.

Can maintenance be modified or terminated? ▼

Yes, on a substantial change in circumstances. Termination is automatic upon the recipient's remarriage. Cohabitation in a resident, continuing, conjugal relationship is also grounds for termination (§510(c)). Modification typically requires proving a material change — a 15% change in either party's income is often a benchmark.

When to Consult an Illinois Family Law Attorney

Illinois maintenance appears formulaic but hides nuance. Consult a licensed IL attorney if your case involves: combined gross above $500,000 (non-presumptive), marriages near 20 years (permanent vs durational decision), self-employment or business income (imputation disputes), complex deductions from net income, or post-judgment modification/termination motions. The interplay with child support under §505 is particularly attorney-dependent.

Illinois Alimony Calculator

How Illinois Maintenance Is Calculated in 2026

Illinois Maintenance Formula

What Counts as "Net Income" in Illinois

The 40% Combined-Net Cap — The Most-Missed Provision

Above $500K Combined Gross Income

Worked Example — 2026

12-Year Marriage, $120K vs $40K Net

Frequently Asked Questions

When to Consult an Illinois Family Law Attorney

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