Alimony in Illinois.
Whether the state sets a formula or leaves it to the judge, what the court has to weigh, how long it runs, and what brings it to an end.
See a different stateIllinois
750 ILCS 5/504(b-1)(1), verbatim: 'If the combined gross annual income of the parties is less than $500,000 and the payor has no obligation to pay child support or maintenance or both from a prior relationship, maintenance payable after the date the parties' marriage is dissolved shall be in accordance with subparagraphs (A) and (B) of this paragraph (1), unless the court makes a finding that the application of the guidelines would be inappropriate. (A) The amount of maintenance under this paragraph (1) shall be calculated by taking 33 1/3% of the payor's net annual income minus 25% of the payee's net annual income. The amount calculated as maintenance, however, when added to the net income of the payee, shall not result in the payee receiving an amount that is in excess of 40% of the combined net income of the parties.' A second, older formula survives for modifications of pre-2019 orders that kept the old tax treatment, s. 5/504(b-1)(1)(A-1), verbatim in relevant part: 'Modification of maintenance orders entered before January 1, 2019 that are and continue to be eligible for inclusion in the gross income of the payee for federal income tax purposes and deductible by the payor shall be calculated by taking 30% of the payor's gross annual income minus 20% of the payee's gross annual income, unless both parties expressly provide otherwise in the modification order.' Note the switch of base: the current formula runs on net income, the legacy one on gross. This is a real guideline, not an advisory one: the words are 'shall be in accordance with', and the only escape is a judicial finding that the guidelines would be inappropriate, which then triggers the findings duty at s. 5/504(b-2)(2). Source: https://www.ilga.gov/legislation/ILCS/details?MajorTopic=&Chapter=&ActName=Illinois%20Marriage%20and%20Dissolution%20of%20Marriage%20Act.&ActID=2086&ChapterID=59&ChapAct=750+ILCS+5%2F&SeqStart=6200000&SeqEnd=8675000
Use the state’s own words
Illinois calls it 'Maintenance'. 750 ILCS 5/504 is captioned 'Maintenance' and 750 ILCS 5/510 'Modification and termination of provisions for maintenance, support, educational expenses, and property disposition'. Illinois also uses 'unallocated maintenance' for a combined maintenance and child support obligation (s. 5/510(c)). The Act does not use 'alimony'.. Using the state’s own term matters when you are searching for forms or reading an order — the words are not interchangeable across state lines, and some of them mean different things in different places.
What the law actually says
The power the court has
What the judge has to weigh
How long it lasts
Duration
750 ILCS 5/504(b-1)(1)(B), verbatim and in full: 'The duration of an award under this paragraph (1) shall be calculated by multiplying the length of the marriage at the time the action was commenced by whichever of the following factors applies: less than 5 years (.20); 5 years or more but less than 6 years (.24); 6 years or more but less than 7 years (.28); 7 years or more but less than 8 years (.32); 8 years or more but less than 9 years (.36); 9 years or more but less than 10 years (.40); 10 years or more but less than 11 years (.44); 11 years or more but less than 12 years (.48); 12 years or more but less than 13 years (.52); 13 years or more but less than 14 years (.56); 14 years or more but less than 15 years (.60); 15 years or more but less than 16 years (.64); 16 years or more but less than 17 years (.68); 17 years or more but less than 18 years (.72); 18 years or more but less than 19 years (.76); 19 years or more but less than 20 years (.80). For a marriage of 20 or more years, the court, in its discretion, shall order maintenance for a period equal to the length of the marriage or for an indefinite term.' Temporary maintenance can be credited against that term, s. 5/504(b-1)(1.5), verbatim: 'In the discretion of the court, any term of temporary maintenance paid by court order under Section 501 may be a corresponding credit to the duration of maintenance set forth in subparagraph (b-1)(1)(B).' And the court must label the award, s. 5/504(b-2)(3), verbatim: 'the court shall state whether the maintenance is fixed-term, indefinite, reviewable, or reserved by the court.' Source: https://www.ilga.gov/legislation/ILCS/details?MajorTopic=&Chapter=&ActName=Illinois%20Marriage%20and%20Dissolution%20of%20Marriage%20Act.&ActID=2086&ChapterID=59&ChapAct=750+ILCS+5%2F&SeqStart=6200000&SeqEnd=8675000
Does behavior matter?
Marital misconduct
Excluded, and the words sit inside the grant of power itself. 750 ILCS 5/504(a), verbatim in relevant part: 'the court may grant a maintenance award for either spouse in amounts and for periods of time as the court deems just, without regard to marital misconduct, and the maintenance may be paid from the income or property of the other spouse.' Verified against the live text of the Act on 2026-08-23. None of the fourteen factors at s. 5/504(a)(1)-(14) is a conduct factor, and none of them reaches dissipation or economic waste either. Illinois puts dissipation in the property division instead, at 750 ILCS 5/503(d)(2), 'the dissipation by each party of the marital property, provided that a party's claim of dissipation is subject to the following conditions', and s. 5/503(d) opens with the same exclusion of fault: the court 'shall divide the marital property without regard to marital misconduct in just proportions considering all relevant factors'. So in Illinois, as in Colorado, fault is excluded from both halves of the financial case. Source: https://www.ilga.gov/legislation/ILCS/details?MajorTopic=&Chapter=&ActName=Illinois%20Marriage%20and%20Dissolution%20of%20Marriage%20Act.&ActID=2086&ChapterID=59&ChapAct=750+ILCS+5%2F&SeqStart=6200000&SeqEnd=8675000
When it ends, and when it can change
What brings it to an end
750 ILCS 5/510(c), verbatim and in full: 'Unless otherwise agreed by the parties in a written agreement set forth in the judgment or otherwise approved by the court, the obligation to pay future maintenance is terminated upon the death of either party, or the remarriage of the party receiving maintenance, or if the party receiving maintenance cohabits with another person on a resident, continuing conjugal basis. An obligor's obligation to pay maintenance or unallocated maintenance terminates by operation of law on the date the obligee remarries or the date the court finds cohabitation began. The obligor is entitled to reimbursement for all maintenance paid from that date forward. Any termination of an obligation for maintenance as a result of the death of the obligor, however, shall be inapplicable to any right of the other party or such other party's designee to receive a death benefit under such insurance on the obligor's life. An obligee must advise the obligor of his or her intention to marry at least 30 days before the remarriage, unless the decision is made within this time period. In that event, he or she must notify the obligor within 72 hours of getting married.' Three things in that paragraph are unusual and easy to miss: termination is 'by operation of law' rather than on motion; the payor is entitled to be paid back everything remitted after the date the court finds cohabitation began, which can be years earlier; and the recipient carries an affirmative 30-day notice duty before remarrying. There is no statutory retirement trigger; retirement reaches maintenance through s. 5/510(a)(1). Source: https://www.ilga.gov/legislation/ILCS/details?MajorTopic=&Chapter=&ActName=Illinois%20Marriage%20and%20Dissolution%20of%20Marriage%20Act.&ActID=2086&ChapterID=59&ChapAct=750+ILCS+5%2F&SeqStart=6200000&SeqEnd=8675000
Changing it later
750 ILCS 5/510(a)(1), verbatim in relevant part: 'upon a showing of a substantial change in circumstances. Contemplation or foreseeability of future events shall not be considered as a factor or used as a defense in determining whether a substantial change in circumstances is shown, unless the future event is expressly specified in the court's order or the agreement of the parties incorporated into a court order.' That second sentence is unusual and is worth stating plainly: in Illinois it is no answer that the change was foreseeable at the time of the judgment. Illinois also requires findings on any adjudicated modification, s. 5/510(c-5), verbatim and in full: 'In an adjudicated case, the court shall make specific factual findings as to the reason for the modification as well as the amount, nature, and duration of the modified maintenance award.' The parties may switch modification off, 750 ILCS 5/502(f), verbatim: 'The parties may provide that maintenance is non-modifiable in amount, duration, or both. If the parties do not provide that maintenance is non-modifiable in amount, duration, or both, then those terms are modifiable upon a substantial change of circumstances.' Source: https://www.ilga.gov/legislation/ILCS/details?MajorTopic=&Chapter=&ActName=Illinois%20Marriage%20and%20Dissolution%20of%20Marriage%20Act.&ActID=2086&ChapterID=59&ChapAct=750+ILCS+5%2F&SeqStart=6200000&SeqEnd=8675000
Worth knowing about Illinois
Illinois is the clearest true-formula state read in this batch: the amount and the duration are both arithmetic, both binding unless the court finds the guidelines inappropriate, and the duration multiplier steps up in one-year bands rather than in the broad brackets other states use. Two features deserve separate notice. First, the designation requirement at s. 5/504(b-2)(3) — fixed-term, indefinite, reviewable, or reserved — makes the label part of the judgment and controls what can be done to the award later; a 'reserved' maintenance judgment keeps the claim alive without ordering any money. Second, the 2019 federal tax change is written into the statute twice: the current formula is stated in net income because maintenance is no longer deductible, and s. 5/504(b-1)(1)(A-1) preserves a parallel gross-income formula for modifying pre-2019 orders that kept the old treatment. Illinois therefore runs two maintenance formulas side by side, divided by 1 January 2019.
The tax rule changed, and most guides still describe the old one
For a divorce or separation instrument executed after 31 December 2018, alimony is not deductible by the person paying it and not taxable to the person receiving it. The Tax Cuts and Jobs Act repealed the provisions that made it otherwise. For an instrument executed on or before that date the old treatment continues — deductible to the payer, taxable to the recipient — unless it is later modified and the modification expressly adopts the new rule.
This is not a detail. Under the old rule a higher-rate payer could transfer income to a lower-rate recipient and the two of them shared the saving. That saving no longer exists, which changes what a given number is worth to each side. New Hampshire wrote the point into its own statute: its 23 per cent figure assumes non-deductibility, and reverts to 30 per cent if the federal treatment is ever restored.
Alongside the federal rule, Illinois’s own income tax follows the federal treatment. That means the federal answer above is the whole answer here — no state adjustment for alimony either way. Four states do not — Arkansas, California, New Jersey and New York — so this is worth knowing rather than assuming. The fifty-state table.
Source: 35 ILCS 5/203(a) (Base income defined – Illinois Income Tax Act) the state source
The other number that decides your budget
How Illinois calculates child support, and the overnight count that moves it more than income does.
And the question underneath it
What Illinois presumes about custody, and what the judge has to weigh.
The rest of what we have written about Illinois. Every figure is quoted from Illinois’s own statute or its courts’ own published schedule, and carries the date we last checked it.