Illinois Spousal Maintenance Calculator: Formula, Duration, and Cap
Illinois Spousal Maintenance Calculator: Formula, Duration, and Cap
Illinois doesn't leave spousal maintenance to guesswork. Since 2019, the state uses a statutory formula under 750 ILCS 5/504 that calculates both the monthly amount and how long payments last. Here's exactly how it works.
The Two-Step Process
Before the formula kicks in, the court must first decide whether maintenance is appropriate at all. A judge evaluates 14 statutory factors — including each spouse's income, earning capacity, age, health, and the standard of living during the marriage. Only after finding that maintenance is warranted does the court apply the guideline formula.
The Illinois Maintenance Formula
The monthly amount uses each spouse's net monthly income:
Monthly Maintenance = (33.3% x Payor's Net Income) minus (25% x Receiving Spouse's Net Income)
For example, if the payor earns $8,000/month net and the receiving spouse earns $3,000/month net:
- 33.3% x $8,000 = $2,664
- 25% x $3,000 = $750
- Monthly maintenance = $2,664 - $750 = $1,914
The 40% Income Cap
There's a built-in ceiling: the receiving spouse's total net income (their own earnings plus maintenance) cannot exceed 40% of the couple's combined net income.
Using the same example: combined net income is $11,000. The 40% cap is $4,400. The receiving spouse's total would be $3,000 + $1,914 = $4,914 — which exceeds $4,400. So the maintenance award gets reduced to $1,400 ($4,400 - $3,000).
When the Formula Applies
The guideline formula is mandatory when:
- Combined gross annual income is under $500,000
- The payor has no prior child support or maintenance obligations from another relationship
For incomes above $500,000, the court has discretion to deviate from the formula.
Duration: How Long Maintenance Lasts
The length of the maintenance award depends on how long the marriage lasted. Illinois uses a multiplier applied to the marriage duration (measured from the wedding date to the date the dissolution petition was filed):
| Marriage Length | Multiplier | Example: 10-Year Marriage |
|---|---|---|
| Under 5 years | 20% | 1 year |
| 5-6 years | 24% | — |
| 6-7 years | 28% | — |
| 7-8 years | 32% | — |
| 8-9 years | 36% | — |
| 9-10 years | 40% | — |
| 10-11 years | 44% | 4.4 years |
| 15-16 years | 64% | — |
| 20+ years | Indefinite or equal to marriage length | — |
For marriages lasting 20 years or more, the court must order maintenance for a period equal to the marriage length or for an indefinite term.
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Temporary vs. Permanent Maintenance
Temporary maintenance can be awarded while the divorce is pending. It keeps the lower-earning spouse financially stable during litigation and uses the same guideline formula.
Reviewable maintenance includes a specific review date. At that point, the court reassesses whether maintenance should continue, be modified, or terminate.
Indefinite maintenance has no set end date and typically applies to marriages of 20+ years.
When Maintenance Automatically Ends
Unless the parties agree otherwise in writing, maintenance terminates upon:
- The death of either spouse
- The remarriage of the receiving spouse
- The receiving spouse cohabitating with another person on a "resident, continuing, and conjugal basis"
Modifying a Maintenance Order
Maintenance can be modified only upon a showing of a "substantial change in circumstances" under 750 ILCS 5/510. This includes involuntary job loss, severe health decline, or retirement at a normal age. Any modification only applies to payments due after the other party receives formal notice of the modification petition — past-due amounts cannot be reduced retroactively.
Maintenance vs. Child Support
These are separate calculations. Child support uses Illinois's Income Shares Model (750 ILCS 5/505), which estimates what both parents would have spent on the child in an intact household and divides that cost proportionally by income. Maintenance addresses the spouse's needs; child support addresses the child's needs. Both can be awarded simultaneously, though courts calculate maintenance first, then child support.
Tax Treatment Since 2019
For divorces finalized after December 31, 2018, maintenance payments are not tax-deductible for the payor and not taxable income for the recipient. This federal change (from the Tax Cuts and Jobs Act) applies to all Illinois maintenance orders.
Running Your Own Numbers
The formula is straightforward, but getting the inputs right — particularly net income calculations using the standardized or individualized tax method — requires careful work. The Illinois Divorce Financial Split Guide includes a maintenance estimator worksheet that walks you through both the amount and duration calculations step by step.
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