Updated for 2026 guidelines
Illinois Maintenance (Alimony) Calculator 2026
Illinois calls it maintenance, and unlike most states it publishes an actual formula: a percentage split of the spouses’ net incomes, a 40 percent cap, and a duration table keyed to the length of the marriage. It applies only under $500,000 of combined gross income, and this tool says so honestly when it does not.
Reviewed by SupportDecode Editorial Team Page content reviewed Sources Methodology Update log
Estimate Illinois guideline maintenance
Estimated monthly maintenance: $2,916.67
The court sets the actual award; this is the statutory formula amount, not a guarantee.
| Line item | Amount |
|---|---|
| Guideline maintenance: 33 1/3 percent of payor net minus 25 percent of payee net (annual)750 ILCS 5/505 (child support) and 5/504 (maintenance) (Illinois General Assembly (ilga.gov)) | $35,000.00 |
| Guideline maintenance, monthly750 ILCS 5/505 (child support) and 5/504 (maintenance) (Illinois General Assembly (ilga.gov)) | $2,916.67 |
Duration limits
- Marriage under 20 years: Duration = length of marriage times the statutory multiplier (0.20 for under 5 years, rising 0.04 per year-band to 0.80 at 19 to 20 years; full table in parameters.maintenance.durationMultipliers).
- Marriage 20 or more years: The court may order maintenance for a term equal to the marriage length or indefinitely.
Guideline duration: 4.4 years (marriage length 10 years times the 0.44 statutory multiplier).
750 ILCS 5/504(b-1)(1)(B)
Assumptions
- Guidelines apply because combined gross annual income is below $500000.
- Child-support interaction (504(b-1)/505): maintenance is calculated first, deducted from the payor net income and added to the payee income for the child support calculation (505(a)(3)(B)/(3)(B-5)).
Estimate only. The court or state agency calculation controls.
Illinois alimony under 750 ILCS 5/504(b-1) (guideline maintenance); 750 ILCS 5/510 (modification), effective 2019-01-01.
How Illinois guideline maintenance works
Most states leave spousal support entirely to the judge. Illinois wrote math into the statute: 750 ILCS 5/504(b-1) sets guideline maintenance at 33 1/3 percent of the paying spouse’s annual net income minus 25 percent of the receiving spouse’s annual net income. The current percentages date from January 1, 2019, when Illinois reworked the formula because federal tax law stopped treating the payments as deductible.
A cap sits on top. The receiving spouse’s own net income plus the maintenance cannot exceed 40 percent of the spouses’ combined net income. When the subtraction produces more than that, the award is trimmed to the cap. With incomes close together, the cap can push guideline maintenance to zero.
The formula has a gate: it applies only when the spouses’ combined gross annual income is under $500,000 and the payor owes no support or maintenance from a prior relationship that changes the picture. At or above the gate, the court sets non-guideline maintenance from the factors in section 504(a). This calculator will not print a number in that situation, because no formula exists there.
Duration is arithmetic too. The length of the marriage is multiplied by a statutory factor that starts at 0.20 for marriages under 5 years and climbs by steps to 0.80 at 19 to 20 years. A 10-year marriage, for example, carries a 0.44 multiplier, so guideline maintenance runs 4.4 years. At 20 years or more, the court may match the length of the marriage or order maintenance indefinitely.
Maintenance and child support interact in a fixed order: maintenance is computed first, then it is deducted from the payor’s net income and added to the recipient’s income before the child support formula runs.
- Formula
- 33 1/3% of payor net minus 25% of payee net, annuallysource
- Cap
- Payee net plus maintenance limited to 40% of combined net incomesource
- Guideline gate
- Applies only under $500,000 combined gross annual incomesource
- Duration
- Marriage length times 0.20 to 0.80; 20+ years can be indefinitesource
- Current formula since
- January 1, 2019 (P.A. 100-923, after the federal tax change)source
- Modification
- Substantial change in circumstances standard, 750 ILCS 5/510source
Worked example: $120,000 and $20,000 net, a 10-year marriage
- Take a paying spouse with $120,000 in annual net income and a receiving spouse with $20,000, married 10 years, with combined gross income of $190,000. The gate is satisfied, because $190,000 is under $500,000, so the guideline formula applies.
- One third of the payor’s net is $40,000. A quarter of the payee’s net is $5,000. Subtracting gives guideline maintenance of $35,000 a year.
- Now the cap check. The payee’s net plus the maintenance is $20,000 plus $35,000, which is $55,000. Forty percent of the combined net of $140,000 is $56,000. Since $55,000 stays under $56,000, the cap does not bite and the full $35,000 stands.
- Monthly, that is $35,000 divided by 12, or $2,916.67.
- Duration uses the 10-to-11-year multiplier of 0.44: ten years times 0.44 gives 4.4 years of guideline maintenance.
The steps above follow the calculation method described on our methodology page.
How to use this estimate
Enter each spouse’s annual net income, meaning income after taxes as Illinois support law defines it, plus the combined gross income of both spouses. The gross figure exists only to test the $500,000 gate; the formula itself runs on the nets.
Add the length of the marriage if you want the duration guidance. The multiplier applies to the length at the date the divorce case was filed, so use that measuring point.
If the result shows the cap was applied, the incomes are close enough that the 40 percent limit is doing the work. Small changes in either income move the number nearly dollar for dollar in that zone.
Remember the formula is the presumption, not a promise. A court must first decide maintenance is appropriate at all, and it can deviate from the guideline with written findings.
What this estimate includes
- The 33 1/3 and 25 percent formula on annual net incomes
- The 40 percent combined-net cap, applied automatically when it binds
- The $500,000 combined-gross gate, with a plain no-formula answer above it
- The statutory duration multipliers, from 0.20 to 0.80 and the 20-year rule
What it leaves out
- Whether maintenance should be awarded at all, which comes before any math
- Net income arithmetic from your tax returns; enter the annual net figures
- Non-guideline maintenance above $500,000, set from the 504(a) factors
- Deviations, agreed waivers, and prenuptial agreement effects
- The child support interaction, which recomputes both incomes afterward
Illinois maintenance FAQs
Is it called alimony or maintenance in Illinois?
Maintenance. The Illinois statute renamed spousal support years ago, and courts and lawyers in the state use that word. This page keeps "alimony" in the title because that is what most people search, but every statutory reference is to maintenance under 750 ILCS 5/504.
What is the Illinois maintenance formula?
Take 33 1/3 percent of the paying spouse’s annual net income, subtract 25 percent of the receiving spouse’s annual net income, and check the cap: the receiving spouse’s net plus the maintenance cannot exceed 40 percent of the combined net. The result is an annual figure, paid monthly.
Why does the calculator refuse when combined income is $500,000 or more?
Because the law does. The 504(b-1) guideline applies only when the spouses’ combined gross annual income is under $500,000. At or above that, Illinois courts set maintenance from the statutory factors, with no formula behind it, so any calculator that prints a number there is making it up.
How long does maintenance last in Illinois?
For marriages under 20 years, the length of the marriage times a statutory multiplier: 0.20 under 5 years, rising in steps of 0.04 per year band to 0.80 at 19 to 20 years. A 6-year marriage carries 0.28, so about 1.7 years. At 20 years or more, the court may order maintenance for the length of the marriage or indefinitely.
Did the 2019 change matter for the amount?
Yes. The earlier guideline ran on gross incomes, in the era when maintenance was tax deductible to the payor. When federal law ended the deduction, P.A. 100-923 switched Illinois to the current 33 1/3 and 25 percent net-income formula effective January 1, 2019. Orders entered under the older version can work differently.
Is guideline maintenance guaranteed if the formula gives a number?
No. The court first weighs the 504(a) factors to decide whether maintenance is appropriate at all. Only after that yes does the guideline amount and duration become the presumptive answer, and the court can still deviate with written reasons.
Can maintenance be changed or ended later?
Yes. Modification and termination of maintenance are governed by 750 ILCS 5/510, which uses a substantial change in circumstances standard and lists the events that end an award. The statute is linked in the sources; the exact effect on any order depends on the judgment’s own terms.
Good to know in Illinois
- The pre-2019 guideline ran on gross incomes, so an older award that does not match today’s formula is not necessarily wrong; it may simply date from the prior law.
- The formula computes an amount, not eligibility. Short marriages with two working spouses often produce a formula result of zero once the 40 percent cap runs.
- When maintenance and child support run in the same case, the maintenance comes first and shifts both incomes before the child support tables apply, so the two awards are linked.
Official sources
Official sources last verified: .
- 750 ILCS 5/505 (child support) and 5/504 (maintenance)
Illinois General Assembly (ilga.gov) Last checked
- 750 ILCS 5/510 (modification and termination of maintenance, support, educational expenses)
Illinois General Assembly (ilga.gov) Last checked
- HFS Child Support Estimator
Illinois HFS Last checked
Reviewed by SupportDecode Editorial Team Page content reviewed Sources Methodology Update log
Changelog: page first published with the 33 1/3 and 25 percent formula, the 40 percent cap, and the $500,000 guideline gate. Material changes are dated in the update log.