Illinois calls alimony maintenance, and for couples under the statute's income limit it follows a formula. If combined gross income is under $500,000 and the payer has no support obligation from a prior relationship, maintenance is 33 1/3% of the payer's net income minus 25% of the recipient's, capped so the recipient doesn't end up with more than 40% of the couple's combined net income.
Duration is formula-driven too, using a multiplier tied to the length of the marriage. But none of that applies until the court first decides that maintenance is appropriate at all. The rules below are from 750 ILCS 5/504, checked in October 2026.
This is a plain-English summary of what the statute says, checked in October 2026. It isn't legal advice, and a family lawyer or your county court's self-help center can tell you how it applies to your case.
Step one: is maintenance appropriate?
Section 504(a) says the court must first decide whether a maintenance award is appropriate, and it does that without regard to marital misconduct. If it finds maintenance isn't appropriate, it bars maintenance regardless of how long the marriage lasted. The factors include:
- Each party's income and property, and their needs.
- Realistic present and future earning capacity of each party.
- Any impairment to earning capacity from domestic duties, or from giving up or delaying education, training or a career because of the marriage.
- The time needed to get education, training and employment.
- The effect of parenting arrangements on a party's ability to work.
- The standard of living during the marriage, the length of the marriage, and each party's age, health and employability.
- Disability and retirement income, and the tax consequences for each party.
Step two: the guideline amount
| Part of the formula | Rule in 504(b-1) |
|---|---|
| Who it applies to | Combined gross annual income under $500,000, and no prior child support or maintenance obligation for the payer |
| Calculation | 33 1/3% of the payer's net annual income minus 25% of the payee's net annual income |
| Cap | The amount plus the payee's net income can't exceed 40% of the couple's combined net income |
| Combined with child support | If maintenance and child support together exceed 50% of the payer's net income, the court may set non-guideline amounts |
The dollar threshold is as of October 2026. Above it, or where the payer already supports a former family, the court sets non-guideline maintenance using the same list of factors and has to explain its reasoning.
Step three: the duration chart
Guideline maintenance lasts for the length of the marriage multiplied by a factor. The statute measures the marriage at the time the case was commenced, so the clock stops at filing.
| Length of marriage | Multiplier |
|---|---|
| Less than 5 years | .20 |
| 5 to 6 years | .24 |
| 8 to 9 years | .36 |
| 10 to 11 years | .44 |
| 15 to 16 years | .64 |
| 19 to 20 years | .80 |
| 20 years or more | Equal to the length of the marriage, or an indefinite term |
The full chart rises by .04 for each extra year between 5 and 20 years. So a 10 year marriage gives 4.4 years of guideline maintenance, while a 20 year marriage can mean maintenance for 20 years or with no fixed end.
Two details worth knowing
Temporary maintenance paid while the case is pending can, at the court's discretion, be credited against the guideline duration. That matters in long cases, because months of temporary support can shorten the final term.
The court also has to say what kind of maintenance it's ordering: fixed-term, indefinite, reviewable, or reserved. Reviewable maintenance comes back to court for a fresh look, so it's worth knowing which label is on your order.
What counts as income in the formula
Section 504(b-3) defines gross income as all income from all sources, using the same meaning as the child support section, Section 505, except that maintenance payments in the pending case aren't counted. Net income also follows Section 505. That's why the same pay slips and tax returns drive both the maintenance and the child support figures.
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The court has to show its working. Under Section 504(b-2), it must state its reasoning for awarding or not awarding maintenance, refer to each relevant factor, and, if it departs from the guidelines, say what the guideline amount or duration would have been and why it varied. A valid agreement between the spouses is one of the listed factors, too.
Orders made before 2019
Illinois keeps a separate calculation for older orders. For orders entered before January 1, 2019 that are modified and keep their old tax treatment, the calculation is 30% of the payer's gross income minus 20% of the payee's gross income, capped at 40% of combined gross income. The IRS confirms the federal side: alimony under agreements executed after 2018 isn't deductible by the payer or taxable to the recipient. If maintenance changes your tax picture, these notes on estimated tax payments may help.
Verdict
Illinois maintenance is predictable for couples under the $500,000 line, because the formula decides both the amount and the length. Run the net income numbers, check the 40% cap, and look up the multiplier for your marriage length. Just don't skip step one: if the court finds maintenance isn't appropriate, the formula never comes into play. Keeping clear records of shared costs, for example in a co-parenting app, helps when parenting arrangements are part of that decision.
Frequently asked questions
How is maintenance calculated in Illinois?
For couples with combined gross income under $500,000 and no prior support obligations, it's 33 1/3% of the payer's net income minus 25% of the payee's, capped so the payee gets no more than 40% of combined net income.
How long does alimony last in Illinois?
Guideline maintenance lasts the length of the marriage multiplied by a factor from .20 for marriages under 5 years up to .80 for 19 to 20 years. For 20 years or more, it can equal the marriage length or be indefinite.
Does adultery affect maintenance in Illinois?
No. Section 504 says the court decides maintenance without regard to marital misconduct.
Is there a minimum marriage length for alimony in Illinois?
No. The duration chart starts at marriages of less than 5 years, but the court must first find that maintenance is appropriate.
What if income is over $500,000 in Illinois?
The guideline formula doesn't apply. The court sets non-guideline maintenance after considering the statutory factors and must explain its reasoning.
