Illinois alimony calculator: how the formula works in 2025

Last updated 2026-07-09

What is the Illinois alimony formula, exactly?

Illinois calls alimony "maintenance," and since 2015 the state has run it through a statutory formula. The formula lives in 750 ILCS 5/504(b-1)(1)(A) ^[1]. Three steps:

Step 1: Take 33.3% of the paying spouse's net annual income. Step 2: Subtract 25% of the receiving spouse's net annual income. Step 3: The result is the annual maintenance amount, unless it pushes the recipient above 40% of the couple's combined net annual income.

Hit that 40% ceiling and the award drops to whatever amount lands the recipient at exactly 40%. The cap keeps maintenance working as a support bridge instead of a wealth transfer.

Net income means gross income minus federal and state income taxes, Social Security, Medicare, mandatory pension contributions, union dues, and health insurance premiums. It is not the take-home number on your pay stub, because some pay-stub deductions come from choices you made (extra 401k contributions, for one). The calculation needs an honest picture of both spouses' actual tax obligations ^[1].

Here's the part people miss. The formula only applies when combined gross income is at or below $500,000 a year. Above that line, the court uses discretion and the formula stops controlling ^[1].

How do you actually run the numbers? A step-by-step example

Say Spouse A earns $90,000 gross and Spouse B earns $30,000 gross. After taxes and other mandatory deductions, Spouse A nets $68,000 and Spouse B nets $24,000.

33.3% of $68,000 = $22,644 25% of $24,000 = $6,000 $22,644 minus $6,000 = $16,644 per year, or $1,387 per month

Now check the 40% cap. Combined net income is $92,000. Forty percent of that is $36,800. Spouse B already has $24,000. The $16,644 award would bring Spouse B to $40,644, which clears the cap. So the award drops: $36,800 minus $24,000 = $12,800 per year, or about $1,067 per month.

The cap bites here. That happens a lot when one spouse earns a decent income and the other earns a modest one.

Now widen the gap. Spouse A nets $120,000, Spouse B nets $10,000. 33.3% of $120,000 = $39,960 25% of $10,000 = $2,500 Formula result: $37,460 per year Combined net: $130,000. Forty percent is $52,000. Spouse B at $10,000 plus $37,460 = $47,460. Under the cap, so the formula result stands: $37,460 per year, roughly $3,122 per month.

That's the math. The hard part is nailing the net income, because that number bends to your specific tax situation. If you're running this yourself, start with last year's tax return, then adjust for any income changes.

How long does maintenance last in Illinois?

Duration is a separate calculation from the amount. Section 750 ILCS 5/504(b-1)(1)(B) sets out a multiplier table keyed to how long you were married ^[1]. The longer the marriage, the bigger the multiplier the court applies to the marriage length.

Marriage length	Duration multiplier	Example
Under 5 years	0.20	5-year marriage = 1 year maintenance
5 to under 6 years	0.24
6 to under 7 years	0.28
7 to under 8 years	0.32
8 to under 9 years	0.36
9 to under 10 years	0.40
10 to under 11 years	0.44	10-year marriage = 4.4 years maintenance
11 to under 12 years	0.48
12 to under 13 years	0.52
13 to under 14 years	0.56
14 to under 15 years	0.60
15 to under 16 years	0.64
16 to under 17 years	0.68
17 to under 18 years	0.72
18 to under 19 years	0.76
19 to under 20 years	0.80
20 years or more	permanent or equal to marriage length, court's discretion

For marriages of 20 years or more, the court picks either permanent maintenance or maintenance that runs as long as the marriage did, whichever it finds appropriate ^[1].

Marriage length runs from the date of marriage to the date you file for divorce, not to the date of judgment. That gap matters if your case drags on a couple of years.

Back to that 10-year marriage from the first example: 10 years times the 0.44 multiplier is 4.4 years of maintenance. Pair it with the formula amount and Spouse B gets roughly $1,067 a month for 4.4 years, then it ends on its own unless someone moves to modify.

What factors can change the formula result?

The formula is a starting point, not the final word. Illinois courts have to weigh a list of factors before deciding whether to order guideline maintenance or go off it ^[1]. The list covers each spouse's income, property, and financial obligations; present and future earning capacity; any earning capacity one spouse lost by putting off education or a career during the marriage; the time the recipient needs to become self-sufficient; the standard of living during the marriage; how long the marriage lasted; the age and health of both spouses; tax consequences; contributions to the other's career; and any valid prenup.

In practice, the formula runs most ordinary-income cases. Deviations show up when one spouse has heavy medical costs, when one spouse takes primary custody of young kids, when the property split is lopsided, or when a spouse owns a business and the income is hard to pin down.

Irregular income (commission sales, seasonal work, self-employment) changes the approach. Courts usually average income over three to five years rather than grabbing a single year. Own a business? Expect the court to comb through distributions, retained earnings, and any personal expenses run through the company.

A prenuptial agreement that addresses maintenance can override the formula outright, if it was properly executed. Illinois adopted the Uniform Premarital Agreement Act, codified at 750 ILCS 10/ ^[2], which decides whether a prenup holds up.

Does Illinois alimony end automatically? What terminates it?

Yes. Maintenance ends automatically on three events under 750 ILCS 5/510(c) ^[9]: the death of either spouse, the recipient's remarriage, or the recipient's cohabitation with a new partner "on a resident, continuing conjugal basis."

Cohabitation termination is not self-executing. The paying spouse has to file a motion and prove it. Courts look at whether the two people share a residence, whether the relationship is romantic, whether they share expenses, and how long it's lasted. There's no magic number of days. Some cases have found cohabitation after a few months; others needed longer.

When the term set in the judgment runs out, maintenance just expires. No motion needed. A recipient who wants to stretch maintenance past the judgment term has to file a petition to extend before it expires, and they carry the burden of proving continued need. Courts are cool to extensions where the recipient had years to become self-supporting and didn't.

Maintenance can also be modified when either party shows a substantial change in circumstances: job loss, serious illness, a big income jump, retirement. The bar is a substantial change, not any change ^[9].

Is Illinois alimony tax deductible in 2025?

No. Since the Tax Cuts and Jobs Act took effect for divorces finalized after December 31, 2018, maintenance is no longer deductible by the payer and no longer taxable income to the recipient ^[3]. This is federal law, and Illinois follows it for divorces finalized in 2019 or later.

That reshapes the math. Before 2019, the payer's deduction cushioned the blow, so courts sometimes ordered larger amounts knowing the payer got a break. Now the gross amount is the payer's true cost and the recipient's true gain. The formula runs on net income, which already reflects taxes paid, so it's built for a post-TCJA world. Just keep the tax difference in mind if you're comparing an old agreement to a current formula result.

Divorces finalized before January 1, 2019 keep the old tax treatment, as long as the decree hasn't been modified to explicitly adopt the new rules ^[10].

The IRS lays this out in Publication 504 ^[3]. Got a divorce from before 2019 and thinking about a modification? Talk to a tax professional before you file anything, because modifying the decree can flip your tax treatment.

What if the spouses agree on a different amount?

Spouses can agree to maintenance that differs from the formula. Uncontested divorce is exactly this: both parties negotiate an amount and duration they can live with, write it into a marital settlement agreement, and ask the court to sign off. Illinois courts generally approve agreements that aren't unconscionable, meaning not wildly unfair and not the product of fraud or coercion.

You can waive maintenance entirely. You can agree to a fixed lump sum instead of monthly checks. You can agree to non-modifiable maintenance (called "contractual" or "in gross"), which means neither party can later ask a court to change it based on changed circumstances. That certainty is worth something when both people want finality.

Handling your own paperwork? The settlement agreement is where all of this gets written down. For a straightforward uncontested case with agreed terms, the divorce papers are the documents you file alongside your petition. The agreement has to be specific: dollar amount, payment schedule, duration, and the events that end it.

DivorceClear's $149 document packet generates a full set of Illinois-specific forms, including the marital settlement agreement, which you can edit to match whatever maintenance terms you and your spouse worked out.

One warning worth repeating: if you waive maintenance in your settlement agreement, that waiver is generally permanent under Illinois law. Hit a financial emergency two years later and wish you'd asked? You usually cannot reopen it. Think hard before you waive.

How does Illinois alimony interact with child support?

Child support and maintenance get calculated separately in Illinois, but they feed each other. Illinois child support uses an income shares model under 750 ILCS 5/505 ^[4], where both parents' incomes drop into a table that sets a presumptive support amount. Maintenance moves those inputs: it counts as income to the recipient parent and comes off the payer's income.

So if you're paying maintenance, your child support gets figured on your income after the maintenance payment. If you're receiving maintenance, that money counts as income in your child support number. The two calculations are chained together.

This gets messy when custody is shared and both parents are trading maintenance and support. Run both calculations carefully, or at least use the Illinois Department of Healthcare and Family Services child support estimator ^[4]. Our child support calculator article walks the income shares model in more detail.

Most uncontested divorces settle the combined maintenance-and-support picture in one settlement agreement and hand the court a single document covering both. Courts like this. It cuts litigation and makes future obligations clear.

What do courts actually award in Illinois? Are there real-world numbers?

Honest answer: there's no statewide dataset on average maintenance amounts or how often courts deviate. The Illinois courts publish aggregate caseload statistics but don't break out average maintenance awards ^[5]. Anyone handing you a confident average is guessing.

Here's what the statute lets us say. In a marriage where the payer nets $80,000 and the recipient nets $20,000, the formula produces about $16,640 a year ($1,387 a month) before the 40% cap check. That's roughly 21% of the payer's net income in this scenario. For a 10-year marriage, it would run about 4.4 years.

Short marriages produce small totals. The under-five-years multiplier is 0.20, so a two-year marriage generates 0.4 years of maintenance. Plenty of attorneys just tell clients in short marriages to negotiate a clean lump sum and move on.

Marriages over 20 years flip the script. The court has full discretion on duration and often orders maintenance that lasts as long as the marriage or runs indefinitely. These are the cases where the stakes get high enough that going it alone carries real risk, and paying for a divorce lawyer consultation is money well spent.

The formula buys predictability. That predictability is what makes uncontested divorce workable for maintenance: both parties can run the numbers on their own, land near the same answer, and negotiate from there instead of fighting over an unknown.

How do you file for maintenance in Illinois? What's the process?

You ask for maintenance in the petition for dissolution of marriage or in a counterpetition. No separate lawsuit for it. The petition just has to request it. If neither party asks for maintenance in the pleadings, the court can't award it later ^[6].

For an uncontested divorce, the process runs like this: file the petition (and counterpetition if both spouses are petitioning), file the marital settlement agreement that spells out the maintenance terms, attend a short prove-up hearing where the judge confirms you both agree and the deal isn't unconscionable, and receive a judgment of dissolution that folds in the agreement.

Filing fees vary by county. In Cook County, the dissolution of marriage filing fee was $388 as of 2024, plus fees for service and other filings ^[7]. Downstate counties usually run lower, often $100 to $250. Check your circuit court's fee schedule, because fees change and swing hard by county ^[7].

The Illinois Courts website at illinoiscourts.gov has self-help resources and links to every circuit court ^[6]. In Cook County, the Domestic Relations Division at the Daley Center runs a self-help center. Many other counties offer similar help.

For a genuinely uncontested case, the paperwork is the hard part, not the courtroom. The prove-up hearing usually takes under 15 minutes if your documents are in order. For the full picture of what you're filing, see our general alimony guide.

Can you modify maintenance after the divorce is final?

Yes. Under 750 ILCS 5/510(a-5) ^[9], either party can petition to modify, suspend, or terminate maintenance after a substantial change in circumstances. The statute names the factors courts weigh: changes in either party's employment, efforts to become self-supporting, tax consequences, property acquired after the judgment, and changes in the recipient's needs.

The key word is substantial. A minor raise doesn't cut it. Neither does a short stretch of unemployment. Courts want a real, lasting change, not a temporary dip.

Retirement is a common trigger. When the payer reaches retirement age and income drops hard, they can petition to reduce or end maintenance. Courts don't cut it automatically. They ask whether the retirement was voluntary and reasonable at that age, and what the actual income drop is.

Order non-modifiable ("in gross") maintenance in your settlement agreement and you both gave up modification rights. The amount and duration lock in no matter what happens to either spouse's finances. That's a trade-off worth chewing on before you sign.

Agreed modifications work too. If both spouses want to change the arrangement after the divorce, they file an agreed order of modification. No contested hearing. This is another spot where doing it yourselves with proper paperwork is doable if the change is simple.

What are the residency requirements before you can file in Illinois?

At least one spouse must have lived in Illinois for at least 90 days right before filing ^[8]. There's no minimum marriage length. You could file the day after your wedding if you've been an Illinois resident for 90 days.

Venue goes to the county where either spouse lives. You live in DuPage County, your spouse lives in Cook County? File in either. Some mild forum-shopping happens here, because Cook County's system is bigger and slower. If speed matters, a smaller county is often faster.

Illinois killed fault-based divorce grounds in 2016. The only ground now is irreconcilable differences ^[8]. You don't allege or prove marital misconduct. That trims the petition down and makes uncontested divorce easier to reach.

For the residency rule, "resident" means domiciled in Illinois, which is more than just being physically present. If you're in Illinois temporarily for work but your permanent home is elsewhere, you may not qualify. This mostly trips up military families and people who just relocated.

Frequently asked questions

Is there an online Illinois alimony calculator I can use?

Yes, several exist, though none are official state tools. The Illinois State Bar Association and various family law firm sites host calculators built on the 750 ILCS 5/504 formula. They're fine for a ballpark. For accuracy you'll need your actual net income figures, not gross pay, since the formula runs on net. Always check results against the statute, because calculators sometimes lag behind legislative amendments.

Does Illinois require you to pay alimony if you were married less than 5 years?

Not automatically. Maintenance is never mandatory; it has to be requested and approved by the court, or agreed to by the parties. For a marriage under five years, the duration multiplier is 0.20, so a four-year marriage generates at most 0.8 years of maintenance under the guideline formula. Courts sometimes decline to order any maintenance for very short marriages unless there's a clear need.

Can a wife be ordered to pay alimony to a husband in Illinois?

Yes. Illinois maintenance law is gender-neutral. The formula runs on relative incomes, not on who is the husband or wife. If the wife earns significantly more, the formula may produce a maintenance obligation running from wife to husband. This shows up more often as income between spouses becomes less predictable.

What happens if my spouse doesn't pay court-ordered maintenance?

Unpaid maintenance becomes a judgment debt. The recipient can file a petition for rule to show cause (contempt of court), seek wage garnishment, or pursue other enforcement remedies under Illinois law. Illinois also lets the court award attorney fees to the party who had to chase enforcement. Courts treat maintenance violations seriously; repeated non-payment can land the payer in jail for contempt.

Does my spouse's new partner's income affect my maintenance?

No, a new partner's income doesn't get added to your spouse's income in the maintenance calculation. But if your spouse moves in with someone and shares expenses, that cohabitation can end maintenance entirely under 750 ILCS 5/510(c). The question isn't whether they have a partner's income, it's whether the living arrangement has cut your spouse's need for support.

How does a prenuptial agreement affect Illinois alimony?

A valid prenup can waive or limit maintenance entirely in Illinois. It has to meet the Illinois Uniform Premarital Agreement Act (750 ILCS 10/). Courts refuse to enforce a prenup signed under duress, without fair disclosure of assets, or that was unconscionable when signed. If a valid prenup waives maintenance, the court generally honors it regardless of what the formula would produce.

What's the difference between temporary and permanent maintenance in Illinois?

Temporary maintenance (pendente lite) is ordered during the divorce to cover the gap between separation and final judgment. It uses the same formula but ends automatically when the final judgment issues. Permanent maintenance has no set end date and runs until death, remarriage, or cohabitation. True permanent maintenance is rare now, mostly reserved for very long marriages or cases where the recipient has no realistic path to self-support.

Does Illinois alimony affect Social Security benefits?

Maintenance is not earned income to the Social Security Administration and generally doesn't reduce SSI the way wages do. But maintenance received can count as unearned income for SSI purposes and may reduce that benefit. For regular Social Security retirement benefits, maintenance doesn't affect your own benefit. SSDI income rules are separate. Check SSA.gov or a benefits counselor for your situation.

How is income calculated for self-employed spouses in Illinois maintenance cases?

For self-employed spouses, net income comes from the business's net profit after legitimate expenses, not gross revenue. Courts often add back personal expenses run through the business, depreciation, and retained earnings that inflate the apparent cost structure. In contested cases, forensic accountants sometimes reconstruct true income. In uncontested cases, spouses usually agree on an income figure and document it in the settlement agreement.

Can maintenance be paid as a lump sum instead of monthly in Illinois?

Yes. Lump-sum maintenance (sometimes called maintenance in gross) is allowed in Illinois. It gives both parties finality. The payer makes one payment and is done; the recipient gets a known amount up front. Lump-sum maintenance is non-modifiable by definition. Courts and spouses sometimes fold lump-sum payments into a property settlement rather than calling them maintenance, especially where tax treatment matters.

How long does it take for an Illinois court to rule on maintenance?

For uncontested divorces with agreed maintenance terms, the prove-up hearing usually lands within a few weeks to a few months of filing, depending on the county's docket. Cook County tends to be slower, often three to six months for routine uncontested cases. Smaller counties may schedule prove-up hearings within four to eight weeks. Contested maintenance hearings take much longer, sometimes a year or more.

Does living together before marriage count toward the marriage length for maintenance?

No. Illinois counts marriage length from the date of the legal marriage, not from when you started living together or dating. Pre-marital cohabitation, even years of it, doesn't stretch the duration multiplier. The date on the marriage license is what counts.

What happens to maintenance if the paying spouse loses their job?

Job loss is possible grounds for modification under 750 ILCS 5/510(a-5), but only if the unemployment is involuntary and the income drop is substantial and likely to last. Courts separate a layoff from voluntary underemployment. If the court thinks the payer cut their income on purpose to dodge maintenance, it can impute income based on earning capacity and deny or limit the modification.

Sources

1. Illinois General Assembly, 750 ILCS 5/504 (Illinois Marriage and Dissolution of Marriage Act, Maintenance section): Illinois maintenance formula: 33.3% of payer's net income minus 25% of recipient's net income, capped at 40% of combined net income; duration multiplier table; formula applies at or below $500,000 combined gross income
2. Illinois General Assembly, 750 ILCS 10/ (Illinois Uniform Premarital Agreement Act): Illinois Uniform Premarital Agreement Act governs enforceability of prenuptial agreements that address maintenance
3. IRS Publication 504, Divorced or Separated Individuals: Under the Tax Cuts and Jobs Act, alimony paid under divorce agreements finalized after December 31, 2018 is not deductible by the payer or taxable to the recipient
4. Illinois Department of Healthcare and Family Services, Child Support Services: Illinois child support uses an income shares model under 750 ILCS 5/505; maintenance payments affect both payer's and recipient's income in the child support calculation
5. Illinois Courts, Annual Report of the Illinois Courts: Illinois courts publish aggregate caseload statistics but do not report average maintenance award amounts
6. Illinois Courts, Self-Help Resources and Circuit Court Directory: Maintenance must be requested in the petition or counterpetition; Illinois Courts website provides self-help resources and circuit court links
7. Clerk of the Circuit Court of Cook County, Fee Schedule: Cook County filing fee for a dissolution of marriage petition was $388 as of 2024
8. Illinois General Assembly, 750 ILCS 5/401 (Illinois Marriage and Dissolution of Marriage Act, Jurisdiction and Grounds): Illinois requires 90-day residency before filing; sole ground for divorce is irreconcilable differences since 2016
9. Illinois General Assembly, 750 ILCS 5/510 (Modification and Termination of Maintenance): Maintenance terminates on death of either party, recipient's remarriage, or recipient's cohabitation on a resident continuing conjugal basis; modification requires substantial change in circumstances
10. IRS, Tax Cuts and Jobs Act: Alimony Changes, IR-2018-232: Divorces finalized before January 1, 2019 retain the old tax treatment for alimony unless the decree is later modified to adopt the new rules