Key takeaways:
- Illinois calls alimony “maintenance.” A judge first decides whether maintenance is appropriate at all, using the factors in 750 ILCS 5/504(a). It is never automatic.
- If maintenance is appropriate and your combined gross income is under $500,000 (and the payer has no support obligation from a prior relationship), the guideline amount is 33 1/3% of the payer’s net income minus 25% of the recipient’s net income.
- That amount is capped: added to the recipient’s own net income, it cannot give the recipient more than 40% of the couple’s combined net income. In many real cases the cap, not the first formula, sets the number.
- Guideline duration is the length of the marriage multiplied by a factor from 0.20 (under 5 years) to 0.80 (19 to 20 years). For marriages of 20 years or more, the court orders maintenance for the length of the marriage or for an indefinite term.
- Maintenance ends on the death of either spouse, the recipient’s remarriage, or the recipient’s cohabitation with another person on a “resident, continuing conjugal basis,” unless a written agreement says otherwise.
Last reviewed: October 22, 2026. This article is general information about Illinois law, not legal advice. Laws change and every situation is different, so talk to a licensed attorney in your state about your own case.
If your marriage is ending in Illinois, you have probably seen alimony numbers online that do not agree with each other. Many sites leave out the 40% cap, round 33 1/3% down to 33%, or describe changes to the law that never happened. This guide walks through the formula exactly as the statute states it, with worked examples you can follow on paper.
Contents
- Who can get maintenance in Illinois
- The guideline formula, step by step
- Worked examples (with the 40% cap)
- Illinois maintenance calculator
- How long maintenance lasts
- When the guidelines do not apply
- Changing or ending maintenance
- FAQ
Who can get maintenance in Illinois
Under 750 ILCS 5/504(a), the court must first make a finding on whether a maintenance award is appropriate. Only if the answer is yes does it move on to the formula. Marital misconduct is not considered. Either spouse can receive maintenance, regardless of gender.
The judge weighs all relevant factors, including:
- each spouse’s income and property, including the property each receives in the divorce;
- each spouse’s needs and realistic present and future earning capacity;
- any impairment of earning capacity because one spouse devoted time to the home or gave up or delayed education, training or career opportunities because of the marriage;
- the time needed for the spouse seeking maintenance to get education, training and employment;
- the effect of parenting arrangements on a spouse’s ability to work;
- the standard of living during the marriage and the length of the marriage;
- age, health, employability, all sources of income (including disability and retirement income) and tax consequences;
- contributions to the other spouse’s education, career or license;
- any valid agreement between the spouses, such as a prenuptial agreement;
- any other factor the court expressly finds just and equitable.
The court must explain its reasoning in writing, refer to the relevant factors, and say whether the maintenance is fixed-term, indefinite, reviewable or reserved (504(b-2)).
Temporary maintenance: a judge can also order maintenance while the divorce is pending (750 ILCS 5/501). In the court’s discretion, time paid under a temporary order can be credited against the guideline duration of the final award (504(b-1)(1.5)).
The guideline formula, step by step
The guidelines in 504(b-1)(1) apply when the court has found maintenance appropriate, the spouses’ combined gross annual income is less than $500,000, and the payer has no child support or maintenance obligation from a prior relationship. Even then, the judge can depart from them by finding that the guidelines would be inappropriate.
- Find each spouse’s net annual income. “Net income” has the same meaning as in the child support statute (750 ILCS 5/505): gross income minus a standardized or individualized tax amount and certain other adjustments.
- Calculate the formula amount: 33 1/3% of the payer’s net income, minus 25% of the recipient’s net income.
- Apply the 40% cap: add the formula amount to the recipient’s net income. If the total is more than 40% of the couple’s combined net income, the maintenance is reduced so the total equals exactly 40%.
- The lower of the two numbers (formula amount or cap amount) is the guideline maintenance.
The cap is not about the payer’s income. It limits what the recipient ends up with: the recipient’s own net income plus maintenance cannot exceed 40% of both spouses’ combined net income. Doing the arithmetic, the cap controls whenever the recipient’s net income is more than about 19% of the payer’s.
Two more rules matter. If guideline maintenance plus child support would exceed 50% of the payer’s net income, the court may set non-guideline maintenance, non-guideline child support, or both. And for orders entered before January 1, 2019 that keep their old tax treatment, modifications use a different gross-income formula (30% minus 20%, with a 40% gross-income cap) under 504(b-1)(1)(A-1).
Worked examples (with the 40% cap)
Example. The payer’s net income is $120,000 a year and the recipient’s is $40,000.
- Formula: 33 1/3% of $120,000 = $40,000. 25% of $40,000 = $10,000. $40,000 minus $10,000 = $30,000.
- Cap: combined net income is $160,000. 40% of that is $64,000. The recipient already has $40,000, so maintenance can be at most $64,000 minus $40,000 = $24,000.
- Guideline maintenance: the lower figure, $24,000 a year ($2,000 a month).
When the recipient has little or no income, the cap usually does not bind. For example, with a payer at $150,000 and a recipient at $0, the formula gives $50,000 and the cap would allow up to $60,000, so guideline maintenance is $50,000 a year.
| Payer net | Recipient net | Formula result | 40% cap limit | Guideline per year | Per month |
|---|---|---|---|---|---|
| $60,000 | $0 | $20,000 | $24,000 | $20,000 | $1,666.67 |
| $80,000 | $20,000 | $21,666.67 | $20,000 | $20,000 | $1,666.67 |
| $100,000 | $30,000 | $25,833.33 | $22,000 | $22,000 | $1,833.33 |
| $120,000 | $40,000 | $30,000 | $24,000 | $24,000 | $2,000 |
| $150,000 | $0 | $50,000 | $60,000 | $50,000 | $4,166.67 |
| $200,000 | $50,000 | $54,166.67 | $50,000 | $50,000 | $4,166.67 |
These are illustrations only. They assume the court has found maintenance appropriate, that the guidelines apply, and that the net incomes are already correctly calculated, which is often the hardest part.
About calculators: the Illinois Department of Healthcare and Family Services (HFS) publishes an official child support estimator, but it is for child support, not maintenance. If you also have children, note that maintenance paid to the other parent is deducted from the payer’s income and included in the recipient’s income when child support is calculated. See our guide to Illinois child support.
Illinois maintenance calculator
Enter yearly net incomes (after taxes and mandatory deductions as defined in 750 ILCS 5/504(b-3)). The calculator applies the guideline formula and the 40% cap from 750 ILCS 5/504(b-1). It only gives the guideline figure: a judge first decides whether maintenance is appropriate at all, and can deviate from the guidelines with written findings.
How long maintenance lasts
Under 504(b-1)(1)(B), guideline duration is the length of the marriage when the divorce was filed, multiplied by a factor:
| Length of marriage | Factor | Length of marriage | Factor |
|---|---|---|---|
| Less than 5 years | 0.20 | 12 to under 13 years | 0.52 |
| 5 to under 6 years | 0.24 | 13 to under 14 years | 0.56 |
| 6 to under 7 years | 0.28 | 14 to under 15 years | 0.60 |
| 7 to under 8 years | 0.32 | 15 to under 16 years | 0.64 |
| 8 to under 9 years | 0.36 | 16 to under 17 years | 0.68 |
| 9 to under 10 years | 0.40 | 17 to under 18 years | 0.72 |
| 10 to under 11 years | 0.44 | 18 to under 19 years | 0.76 |
| 11 to under 12 years | 0.48 | 19 to under 20 years | 0.80 |
For a marriage of 20 years or more, the court, in its discretion, orders maintenance either for a period equal to the length of the marriage or for an indefinite term.
Examples: a 4-year marriage gives 4 x 0.20 = 0.8 years, about 9.6 months. A 12-year marriage gives 12 x 0.52 = 6.24 years, about 75 months. A 15-year marriage gives 15 x 0.64 = 9.6 years, about 115 months.
Illinois law also describes how an award is labeled. Fixed-term maintenance ends on a set date and cannot be extended. Reviewable maintenance runs for a set term and is then reviewed, when the court can extend it, make it fixed or indefinite, or terminate it. Indefinite maintenance has no end date and continues until modified or terminated under Section 510.
When the guidelines do not apply
- Combined gross income of $500,000 or more, or a payer with support obligations from a prior relationship: the formula does not apply, and the court sets any award by weighing the 504(a) factors.
- The court finds the guidelines inappropriate: it can deviate, but it must state what the guideline amount or duration would have been and why it varied.
- Maintenance plus child support over 50% of the payer's net income: the court may set non-guideline amounts.
- A valid prenuptial or marital agreement may control, subject to the court's review.
Changing or ending maintenance
Under 750 ILCS 5/510, unless a written agreement in the judgment says otherwise, future maintenance ends on:
- the death of either spouse;
- the recipient's remarriage; or
- the recipient's cohabitation with another person on a resident, continuing conjugal basis.
The obligation ends by operation of law on the date of remarriage or the date the court finds cohabitation began, and the payer is entitled to reimbursement of maintenance paid after that date. The recipient must tell the payer about a planned remarriage at least 30 days ahead, or within 72 hours of the wedding if the decision is made later. The statute does not set a minimum length of cohabitation; whether a relationship qualifies is decided by the court based on the facts.
Otherwise, a maintenance order can be modified or terminated only after a substantial change in circumstances. The court considers factors such as whether a change in employment was made in good faith, the recipient's efforts to become self-supporting, changes in income and property since the judgment, and how much maintenance has already been paid relative to the length of the marriage. Fixed-term maintenance, once its period ends, is barred.
Unpaid maintenance is a judgment. Each missed installment becomes a judgment against the payer, accrues interest, and creates a lien on the payer's property (504(b-5) and (b-7)).
FAQ
How is alimony calculated in Illinois?
If the court finds maintenance appropriate and the guidelines apply, it takes 33 1/3% of the payer's net income minus 25% of the recipient's net income. The result is capped so the recipient's net income plus maintenance does not exceed 40% of the couple's combined net income.
Is alimony automatic in Illinois?
No. The court first decides whether maintenance is appropriate by weighing the factors in 750 ILCS 5/504(a), such as income, needs, earning capacity, the standard of living and the length of the marriage. If it is not appropriate, maintenance is barred.
How long is alimony paid after 15 years of marriage in Illinois?
Under the guidelines, a marriage of 15 years or more but less than 16 years uses a factor of 0.64. Fifteen years times 0.64 is 9.6 years, or about 115 months. The court can deviate if it explains why.
What ends maintenance in Illinois?
Unless a written agreement says otherwise, maintenance ends on the death of either spouse, the recipient's remarriage, or the recipient's cohabitation with another person on a resident, continuing conjugal basis. Otherwise it can be modified only after a substantial change in circumstances.
Sources: 750 ILCS 5/504 (maintenance); 750 ILCS 5/510 (modification and termination); 750 ILCS 5/505 (net income definition); 750 ILCS 5/501 (temporary relief); Illinois HFS child support estimator.
