Illinois — Corporate Income / Franchise Tax

Illinois imposes income tax on corporations (other than S corporations) for the privilege of earning or receiving income in or as a resident of Illinois. The tax applies to C corporations doing business in Illinois or earning Illinois-source income. S corporations are exempt from Illinois corporate income tax but remain subject to the replacement tax at a different rate.

In addition to the 7 percent corporate income tax, corporations must pay a 2.5 percent Personal Property Replacement Tax on net income, resulting in a combined effective rate of 9.5 percent. The replacement tax was enacted to compensate local governments for the elimination of personal property taxes on business assets.

Corporations must file Form IL-1120 if they are either liable for tax under the Illinois Income Tax Act or qualified to do business in Illinois, regardless of tax liability.

Source: 35 ILCS 5/201 and Illinois Department of Revenue - Corporation Tax Information

Illinois imposes corporate income tax and replacement tax on corporations, including nonresident corporations, when they earn or receive income in Illinois and have nexus as defined by the U.S. Constitution. As of July 2026, Illinois continues to assert the broadest jurisdiction permitted by the Due Process and Commerce Clauses, rather than establishing a specific receipts, property, or payroll threshold for income tax nexus.

Inventory, in-state property, and physical presence: Per recent Illinois Department of Revenue General Information Letter IT-26-0001-GIL (May 14, 2026), physical presence within Illinois—such as ownership of inventory stored in an in-state third-party contract packager's facility—can be sufficient to establish income tax nexus, regardless of whether salespeople or offices are present. This applies even if the taxpayer is protected from sales tax nexus or the transactions are conducted by an independent contractor. (This clarification is supplemental to prior guidance under 86 Ill. Adm. Code § 100.9720, which already recognized that nonresident corporations can have nexus on the basis of in-state property, payroll, or activities that generate Illinois-source income. For property, mere presence of inventory or business assets in Illinois subjects the owner to tax.)

No economic or factor presence threshold for income tax: Unlike Illinois sales/use tax, which applies explicit economic nexus thresholds ($100,000 in sales or 200 transactions per year), the state has not enacted receipts, payroll, or property thresholds for corporate income tax nexus. The Department asserts tax jurisdiction to the constitutional limit, relying on the presence of income derived from or attributable to Illinois sources and related business activities.

Combined groups and Finnigan apportionment (effective tax years ending on or after December 31, 2025): For unitary business groups, Illinois has adopted the Finnigan method for income tax apportionment and reporting (Public Act 104-0006, as implemented by amended 86 Ill. Adm. Code § 100.5270). Under Finnigan, all Illinois sales of group members are counted in the numerator of the sales factor for apportionment, even if the specific member with sales has no separate nexus with Illinois. This is a material shift from the prior Joyce method, where only sales by members with Illinois nexus were included. Practitioners must note that the combined group filing requirement and Finnigan apportionment may bring members with no direct Illinois connection into the group's Illinois apportionment base for income tax purposes.

Filing requirement: Corporations must file Form IL-1120 if they are liable for Illinois income or replacement tax or are qualified to do business in Illinois and required to file a federal return, regardless of actual tax liability for the year.

References updated June 2026 for recent regulatory and interpretive changes affecting corporate income tax nexus and apportionment.

Source: 86 Ill. Adm. Code § 100.9720 Source: Illinois Department of Revenue GIL IT-26-0001-GIL (2026) Source: Public Act 104-0006 / 86 Ill. Adm. Code § 100.5270 Source: 35 ILCS 5/502(a)

Note: The previously cited URLs for GIL IT-26-0001-GIL and 35 ILCS 5/502(a) were updated as of June 2026 to replace broken links with currently functioning official sources. The citation to 86 Ill. Adm. Code § 100.9720 remains unchanged, as its official link is still available at ilga.gov. If any official URL to an administrative rule becomes unavailable in the future and no .gov replacement is found, the citation text will be retained but the dead link will be noted for remediation.

Illinois imposes a 7 percent corporate income tax on net income for taxable years beginning on or after July 1, 2017. In addition, corporations (other than S corporations) are subject to a 2.5 percent Personal Property Replacement Tax on the same net income base, resulting in a combined effective rate of 9.5 percent.

Source: 35 ILCS 5/201(b)(14); 35 ILCS 5/201(d); Illinois Department of Revenue - Income Tax Rates

Illinois apportions the business income of multistate corporations using a single sales factor formula. The apportionment percentage equals Illinois sales divided by total sales everywhere. Sales of tangible personal property are sourced to Illinois if delivered or shipped to a purchaser within Illinois. For sales other than tangible personal property, Illinois applies market-based sourcing rules under Section 304(h), which generally assign receipts to Illinois based on where the service is received or the intangible is utilized.

Different apportionment formulas apply to insurance companies (Section 304(b)), financial organizations (Section 304(c)), federally regulated exchanges (Section 304(c-1)), and transportation companies (Section 304(d)).

Source: 35 ILCS 5/304(a); 35 ILCS 5/304(h)

Corporate returns are due on or before the 15th day of the third month following the close of the taxable year. Illinois applies the same due date as federal returns when a taxpayer's income or loss is reported for federal purposes on a return with a later due date. For calendar-year C corporations, Form IL-1120 is due April 15. Illinois provides an automatic six-month extension to file without requiring a separate extension form, though any tax owed must be paid by the original due date to avoid interest and penalties.

Source: 35 ILCS 5/505(a)(1); Illinois Department of Revenue - Corporation Tax Information

Illinois corporate income tax starts with federal taxable income and applies a prescribed list of additions and subtractions under Section 203(b) of the Illinois Income Tax Act to determine "base income." This calculation governs both C corporations and specified entities like life insurers, RICs, and REITs (see 35 ILCS 5/203(b)(1), subsections E–G). The set of modifications is governed by both statutory law and annual guidance from the Illinois Department of Revenue, most recently reflected in Informational Bulletin FY 2026‑15, which introduces key adjustments for tax years ending on or after December 31, 2025.

Starting point: federal taxable income (35 ILCS 5/203(b)(1))

• C corporations begin with federal taxable income as reported on U.S. Form 1120.
• Specialized entities begin with their federal taxable income as defined for their category (e.g. life insurance, REIT, RIC).

Material new additions and subtractions for tax year 2026 forward

• Interest expense limitation conformity (IRC § 163(j)): Illinois now requires a new adjustment for interest deduction carryforwards/allocations, conforming more closely to IRC § 163(j) mechanics for taxable years ending on or after December 31, 2025.
• Endowment gifts/Illinois Gives Tax Credit: For tax years ending on or after December 31, 2025, a new addition is required for income deducted federally that relates to the Illinois Gives endowment contribution credit. This is directly reflected on a new line on Schedule M (Other Additions and Subtractions), pursuant to Informational Bulletin FY 2026‑15.
• NCTI deduction (foreign dividends): Effective for tax years ending on or after December 31, 2025, the deduction for net controlled foreign corporation income is limited to 50% per Illinois Schedule J, per Department instructions.

Key continuing modifications under 35 ILCS 5/203(b)(2):

• Interest income from non-Illinois state and municipal bonds (addback, 5/203(b)(2)(A)).
• IRC § 250 deduction (FDII/GILTI): Add back any deduction claimed federally (5/203(b)(2)(E-14)).
• Bonus depreciation/Section 179: Add back federal bonus depreciation (IRC § 168(k)) and, for property placed in service after Jan. 1, 2026, also add back IRC § 168(n) bonus depreciation (5/203(b)(2)(E-13)).
• Related-party and 80/20 addbacks, certain federal credits, and pass-through adjustments remain as described in the current statute, noting new form lines may be added or nomenclature updated annually by the Department.

Subtraction modifications (Selected examples):

• Interest from U.S. government obligations and certain U.S. territory securities (5/203(b)(2)(I), (M)).
• Depreciation subtraction: Regular (non-bonus) depreciation recovery for property with bonus depreciation addback (5/203(b)(2)(D-10)).
• Corresponding related-party subtractions (E-11).
• Pass-through subtractions as reported on K-1-P/IL-1120.

Enumerated-only modifications policy Section 203(h) affirms that base income modifications are strictly limited to those listed; neither taxpayers nor the Department can create new ones.

Reporting and forms updates

• Modifications are reported on Schedule M and, for NCTI, on Schedule J (2026 version limits deduction to 50%).
• Schedule M for 2026 includes a new line for endowment-gift/Illinois Gives addbacks.
• Form and line references may change with each Department bulletin; practitioners must monitor for annual form/instruction updates.

Updated for Bulletin FY 2026‑15 and related law and form changes effective for tax years ending on or after December 31, 2025.

Source: 35 ILCS 5/203 Source: Illinois Department of Revenue - Corporation Tax Information Source: Illinois Form IL-1120 Instructions Source: Illinois Informational Bulletin FY 2026-15

Illinois allows corporations to deduct net operating losses (NOLs) under Section 207 of the Illinois Income Tax Act, but the carryback and carryforward periods, and the ability to use those losses, differ significantly from federal rules and have changed multiple times over the past two decades. Practitioners must identify when the loss was incurred and when it is being used to determine the applicable carryforward period and any annual deduction cap.

How Illinois net losses are computed

An Illinois net loss arises when, after applying all Section 203(b)(2) addition and subtraction modifications and the Article 3 allocation and apportionment rules, the taxpayer's net income results in a loss. This means the taxpayer starts with federal taxable income, applies the Illinois-specific modifications (such as adding back bonus depreciation and the Section 250 FDII deduction, and subtracting U.S. government interest), and then apportions or allocates the resulting base income—if that number is negative, it is an Illinois net loss available for carryover under Section 207.

Illinois net losses are distinct from federal NOLs. A corporation may have a federal NOL but not an Illinois net loss (or vice versa) because Illinois applies different modifications and a different apportionment formula. The Illinois net loss is computed on Illinois Schedule NLD.

Carryforward and carryback periods: depends on when the loss was incurred

The Illinois Income Tax Act has changed the carryback and carryforward periods multiple times. The applicable rules depend on the taxable year in which the loss was incurred:

• Losses incurred in taxable years ending before December 31, 1999: Carryback and carryforward allowed in the manner permitted under IRC Section 172 as it existed at that time.
• Losses incurred in taxable years ending on or after December 31, 1999, and before December 31, 2003: Two-year carryback and 20-year carryforward. A taxpayer could elect to relinquish the entire carryback period and carry the loss forward only; the election had to be made by the due date (including extensions) of the return for the loss year and was irrevocable once made.
• Losses incurred in taxable years ending on or after December 31, 2003, and before December 31, 2021: No carryback; 12-year carryforward. (An optional carryback election was available for losses incurred in taxable years ending on or after December 31, 2003, and before December 31, 2019, but the default rule was no carryback.)
• Losses incurred in taxable years ending on or after December 31, 2021: No carryback; 20-year carryforward.

A legislative change in 2021 (Public Act 102-0658) retroactively extended the carryforward period from 12 years to 20 years for any unexpired loss as of November 16, 2021.

Order of application: carrybacks first, then carryforwards in order of expiration

When a carryback is permitted (for losses incurred in taxable years ending 1999–2002), the loss must be carried back to the earliest of the two preceding taxable years before it may be carried forward. When multiple losses are available in a single taxable year, Illinois net losses are applied in order of expiration, beginning with the oldest loss first. This rule is consistent with federal ordering.

Corporate limitation: annual cap on NOL deduction

For C corporations (other than S corporations), Illinois law imposes a limitation on the amount of NOL that may be claimed in specific taxable years, regardless of the total carried-forward NOL balance:

• Taxable years ending on or after December 31, 2010, and before December 31, 2012: NOL deduction suspended (zero allowable deduction).
• Taxable years ending on or after December 31, 2012, and before December 31, 2014: NOL deduction capped at $100,000.
• Taxable years ending on or after December 31, 2021, and before December 31, 2024: NOL deduction capped at $100,000 (per Public Act 102-0016).
• Taxable years ending on or after December 31, 2024, and before December 31, 2027: NOL deduction capped at $500,000 (Public Act 103-0592, codified at Section 207(d)(3)).

These limitations apply only to the deduction year (the year in which the loss is claimed), not the loss year. S corporations are not subject to the cap.

Critical rule: cap and suspension years do not count against the carryforward period

Section 207(d) provides that “for purposes of determining the taxable years to which a net loss may be carried under subsection (a) of this Section, no taxable year for which a deduction is disallowed under this subsection, or for which the deduction would exceed the applicable annual limitation if not for this subsection, shall be counted.” The carryforward clock effectively pauses during suspension and cap years.

Federal NOL deduction must be added back on the Illinois return

Illinois computes net losses under its own rules, so any federal NOL deduction claimed must be added back under Section 203(b)(2)(D). The Illinois NOL deduction is computed separately using Illinois Schedule NLD and flows to Form IL-1120.

Filing mechanics

Corporations claim the Illinois NOL deduction using Illinois Schedule NLD, reporting each year’s loss, usage, and remaining balance. No refund or credit will be issued for a return filed more than three years past the extended due date of the loss-year return (though the loss itself may still be used to offset future income, subject to the carryforward period).

Cessation of business

If a corporation with an Illinois NOL ceases Illinois activity, the loss may be claimed if the corporation resumes operations within the carryforward window, per General Information Letter IT 13-0007-GIL.

Reduction for discharge of indebtedness income applies as described in Section 207(c).

Source: 35 ILCS 5/207 Source: Illinois Department of Revenue – What are the limitations for using an Illinois Net Operating Loss? Source: Illinois Department of Revenue – IDOR Q&A on NOL corporate cap Source: Illinois Informational Bulletin FY 2025-01 Source: Public Act 103-0592 amending Section 207

Effective for tax years beginning on or after January 1, 2026, Illinois requires corporations to add back to base income any amount of federal 100 percent bonus depreciation claimed under Internal Revenue Code § 168(n), as well as § 168(k). Public Act 104-0453 amended Section 203 of the Illinois Income Tax Act (IITA) to require this new addition modification for corporations, aligning the treatment of 168(n) property with that previously applicable to 168(k).

Statutory amendment details: The amended IITA Section 203(b)(2)(E-13) provides that taxpayers must add to their federal taxable income "an amount equal to any additional depreciation deduction allowed under Section 168(n) of the Internal Revenue Code... for property placed in service in such taxable year for federal income tax purposes." This applies to property that qualifies for bonus depreciation under the new federal provision—generally, qualified production or manufacturing property eligible under IRC § 168(n), which, as of its effective date, allows a 100% immediate deduction for certain investments as enacted by federal law.

Mechanical treatment and recovery: As with bonus depreciation under 168(k), Illinois requires the addback in the year the bonus is claimed federally. The cost is then recovered over time through subtraction modifications reflecting the normal depreciation schedule as if the property had not qualified for 168(n) bonus treatment. This process is reported on Illinois Form IL‑4562, Special Depreciation, which allows the taxpayer to subtract the regular depreciation amount each year over the asset’s applicable federal recovery period.

From the Department of Revenue’s Informational Bulletin FY 2026-15: "For tax years beginning on or after January 1, 2026, Public Act 104-0453 amended Section 203 of the IITA to decouple Illinois from federal 100 percent bonus depreciation claimed under IRC Section 168(n). Use Form IL-4562, Special Depreciation, Line 16 to include the amount of federal depreciation you would have claimed on your federal return for property for which you elected the bonus depreciation under Section 168(n) had you not made the election."

Summary:

• Applies to property for which federal bonus depreciation is claimed under IRC § 168(n), effective for tax years beginning January 1, 2026.
• Requires full addback in year bonus depreciation is claimed, with phased subtractions over asset’s depreciable life following federal regular depreciation schedule.
• Mechanics are set out in amended IITA Section 203, with reporting on IL-4562, Line 16.

Source: Public Act 104-0453 amending IITA Section 203 Source: Illinois Informational Bulletin FY 2026-15

Illinois requires corporations that are part of a unitary business group to file Illinois corporate income tax returns on a unitary combined basis. A unitary business group is defined at 35 ILCS 5/1501(a)(27) as a group of entities related through common ownership (more than 50% of voting stock, directly or indirectly), engaged in a unitary business (sufficient operational integration, central management, economies of scale), including LLCs taxed as corporations for federal purposes. Entities with "80% or more business activity outside the United States" (an 80/20 company) are excluded from the Illinois group per statute.

2025–2026 changes: Finnigan method and new filing mechanics

• Finnigan apportionment required: For tax years ending on or after December 31, 2025, Illinois adopts the Finnigan method for sales factor apportionment (Public Act 104-0006, codified in amended 86 Ill. Adm. Code § 100.5270; confirmed by IDOR Informational Bulletin FY 2026-15). Under Finnigan, all Illinois sales by combined group members are included in the Illinois numerator, even if the selling member lacks Illinois nexus. This replaces the Joyce method, which included only Illinois-nexus members’ sales, and materially expands the Illinois apportionment base for many groups.

• Throwback/throwout rules: Groups must also apply the throwback/throwout rules on a post-combination basis (i.e., after summing sales for the combined group).

• Revised Schedule UB mechanics: The Illinois Schedule UB (Unitary Business Group Combined Return) was updated in March 2026 to require a new Allocation Worksheet for groups that include members not taxable in Illinois. This worksheet allocates group income and sales factor between members taxable in Illinois and those that are not. Practitioners must carefully complete all new lines and sub-schedules—including subgroup and exclusion entries—based on the 2025–26 Schedule UB instructions from the Department of Revenue.

• Exclusions and transition: S corporations, partnerships, insurance companies, and foreign affiliates meeting the 80/20 test are not included in the combined group. Entities acquired or divested during the year are generally included only for the period(s) when they met group criteria. Special computational mechanics, as defined in 86 Ill. Adm. Code § 100.5270 and the updated Schedule UB instructions, apply to new combinations, acquired/disposed entities, and subgroups.

• Net loss deduction and limitations: For tax years ending after December 31, 2024, the Illinois Net Loss Deduction (NLD) mechanics for combined groups are determined and allocated on Schedule UB/NLD, with an updated $500,000 cap and carryforward allocation rules, effective per Public Act 103-0592.

Practitioner note: All groups filing a combined return for taxable periods ending after December 31, 2025, must apply the Finnigan method, use the revised Schedule UB Allocation Worksheet, and follow the latest guidance for Schedule UB/NLD and loss limitations. Failure to account for these changes may result in material reporting errors.

Material law changes and form instruction updates effective for tax years ending on or after December 31, 2025 are incorporated above.

Source: 35 ILCS 5/1501(a)(27) Source: 35 ILCS 5/304(e) Source: Public Act 104-0006 (Finnigan method) Source: 86 Ill. Adm. Code § 100.5270 Source: Illinois Schedule UB instructions (2025–26) Source: Illinois Informational Bulletin FY 2026-15 Source: Illinois Form IL-1120 Schedule UB/NLD Instructions

Illinois requires corporations to make quarterly estimated income and replacement tax payments if the corporation expects its total tax liability (net of allowable credits and including the replacement tax) to be more than $400 for the year. If the annual liability is expected to be $400 or less, no estimated payments are required for that year. This applies to C corporations as well as S corporations with a replacement tax liability exceeding the threshold.

Quarterly due dates: Estimated payments must be made in four installments. For calendar-year taxpayers, the due dates are:

• First installment: April 15
• Second installment: June 15
• Third installment: September 15
• Fourth installment: December 15

Fiscal-year taxpayers make payments on the 15th day of the fourth, sixth, ninth, and twelfth months of their fiscal year. Payments are made using Illinois Form IL-1120-ES (Estimated Income and Replacement Tax Payment for Corporations).

Safe harbor methods to avoid underpayment penalty: Corporations may avoid underpayment penalties if their estimated tax payments (including any prior-year overpayment credit) meet one of the following safe harbors:

• Equal at least 90% of the final tax liability (including replacement tax) for the current tax year, or
• Equal at least 100% of the tax liability shown on the return for the preceding tax year, provided the prior year was a full 12 months and a return was filed (if the prior year’s liability was $400 or less, this safe harbor is not available).

If estimated payments are insufficient and the safe harbor is not met, Illinois may assess a penalty for underpayment. The penalty accrues on the unpaid portion of the required installment from the installment due date to the date the installment is paid or the return is filed, whichever is earlier. Corporations may request a waiver if the underpayment was due to reasonable cause.

References and mechanics:

• The estimated payment threshold, calculation, due dates, and rules are governed by 35 ILCS 5/803, 5/804, and Illinois Administrative Code Title 86, Section 100.8010.
• Official guidance is available from the Illinois Department of Revenue: “You must make estimated payments if you expect your tax liability... to be more than $400 for the tax year. ...The penalty is avoided if you pay at least 90% of your actual tax liability for the year or 100% of your prior year tax liability.”

Source: 35 ILCS 5/803 Source: 86 Ill. Adm. Code 100.8010 Source: Illinois Department of Revenue – Business Income Tax Estimated Payments

Effective January 1, 2026, Illinois has fully repealed its corporate franchise tax. No franchise tax liability is imposed on corporations for any event (initial, annual, or additional for paid-in capital increases) occurring on or after January 1, 2026. This repeal was enacted by HB 5490 (103rd General Assembly), amending the Business Corporation Act of 1983 (805 ILCS 5/15.35, 15.65, 15.97) and follows the phase-out that began with the $10,000 exemption for tax years 2025 and 2026.

Key points for 2026 and later:

• As of January 1, 2026, there is no longer any franchise tax due, assessed, or required to be paid for any transaction or filing.
• Corporations must still comply with all applicable Illinois Secretary of State filing requirements (such as Annual Reports/BCA 14.05 and paid-in capital amendments), but only the statutory filing fees are due — not franchise tax calculated on paid-in capital.
• The final year for any franchise tax liability was 2025, which itself was subject to the $10,000 exemption. Taxes due for franchise tax events occurring before January 1, 2026 (including late or amended filings for earlier periods) must have been paid as scheduled. After January 1, 2026, no franchise tax may be assessed for any period.

Legislative background:

• The original franchise tax was imposed under 805 ILCS 5/15.35 et seq. and required payment on a corporation’s paid-in capital, with annual, initial, and “additional” taxes for capital increases.
• Repeal was accomplished via HB 5490 (2024), which fully repealed all remaining franchise tax provisions effective January 1, 2026.

Practitioner note: Illinois corporations and foreign corporations registered to do business in Illinois must continue all Secretary of State filings necessary to maintain good standing, including annual reports and changes in capital structure, but after January 1, 2026, the franchise tax is obsolete and the obligation is limited to the statutory fees.

Source: Public Act 103-XXXX (2024) repealing franchise tax provisions, amending 805 ILCS 5/15.35, 5/15.65, 5/15.97

Illinois does not impose corporate income or replacement tax on out-of-state corporations based solely on crossing a receipts-based economic or "factor presence" threshold. Unlike its sales and use tax regime—where, following South Dakota v. Wayfair, Inc., out-of-state sellers exceeding $100,000 in Illinois sales or 200 transactions are required to collect tax—Illinois does not apply a similar objective receipts or transactions threshold for corporate income tax purposes.

No statutory receipts or transaction threshold for income tax Illinois law (35 ILCS 5/201; 86 Ill. Adm. Code § 100.9720) imposes tax on corporations "earning or receiving income in or as a resident of Illinois." Regulatory language and Department interpretations confirm that, unlike some states that use explicit "factor presence" standards (such as $500,000 Illinois sales or X% property/payroll), Illinois has not established a numerical test based solely on Illinois gross receipts. Instead, the Department asserts nexus to the constitutional limit, considering both physical presence and sustained economic activity that gives rise to Illinois-source income.

86 Ill. Adm. Code § 100.9720 provides: "Any person, not a resident of Illinois, who derives income from or attributable to sources within Illinois is subject to tax, provided such person has sufficient nexus with Illinois to satisfy the requirements of the Constitution of the United States." The presence of receipts alone, without further activity or connection, is not determinative for income tax registration or filing duty. Department guidance and published regulations do not provide for an objective receipts threshold.

Distinction from sales/use tax Illinois’ income tax approach contrasts with its clear economic nexus rule for sales/use tax, located at 35 ILCS 105/2(1), which imposes collection and remittance obligations based on a $100,000 or 200-transaction threshold. There is no parallel threshold for corporate income tax as of June 2026.

Source: 86 Ill. Adm. Code § 100.9720 Source: 35 ILCS 5/201

Not yet human confirmed.

Illinois employs market-based sourcing for apportioning receipts from services and most intangibles for corporate income tax, but as of mid-2026, the Illinois Department of Revenue (IDOR) has not promulgated detailed regulations or issued binding General Information Letters addressing the precise treatment of SaaS, hosted/cloud software, or digital goods for sales factor purposes.

Statutory and general framework—market-based sourcing:

• Statutes at 35 ILCS 5/304(a)(3)(C-5) and 5/304(h) provide the basis for Illinois’s market-based sourcing regime: receipts from services are included in the Illinois sales factor numerator if the service is received in Illinois, and receipts from intangibles are sourced based on utilization in the state.

Department position and practitioner interpretation:

• In Private Letter Ruling IT-14-0003 (2014), the Department treated cloud hosting, SaaS, and remote software provision as “services,” not as transfers of intangible property, and therefore subject to the service-sourcing rules under Section 304(h). While PLRs are not binding precedent and apply only to the taxpayer that requested them, IT-14-0003 is frequently cited by practitioners as the Department’s practical position.
• No published administrative rule, General Information Letter, or income tax-specific audit manual covers SaaS or cloud software apportionment as of mid-2026. Observationally, Illinois audit practice follows the statutory hierarchy—sourcing SaaS/cloud receipts to Illinois if the customer receives the benefit in Illinois or, if indeterminate, to the customer's billing address in line with the fallback provisions in 35 ILCS 5/304(h).
• While the Department has responded in sales tax contexts (see, e.g., ST-23-0017-GIL) that cloud software and SaaS are considered services based on where the customer receives the benefit, this guidance is not directly controlling for income tax apportionment but does reflect a parallel in Department reasoning about the character of SaaS transactions.

Practical caution and documentation:

• Given the absence of binding, category-specific income tax rules, filers apportioning receipts from SaaS or digital platforms should explicitly document their basis for treating such receipts as service income, retain support for the location of customer use or benefit, and consider requesting private guidance from IDOR for novel or high-dollar situations.
• There is no published industry-wide consensus on precise documentation or audit substantiation standards for SaaS income tax apportionment in Illinois.

Summary:

• Illinois’s statutory framework and available Department letter rulings support sourcing SaaS, cloud, and digital goods receipts to Illinois if the customer receives/accesses the service in Illinois. However, there is no directly binding regulation or comprehensive audit manual addressing SaaS receipt sourcing for corporate income tax as of mid-2026. Observed Department practice relies on general market-based sourcing rules and parallels to sales tax treatment.

Source: 35 ILCS 5/304(a)(3)(C-5), (h) Source: Illinois Dept. of Revenue PLR IT-14-0003 (2014) Source: Illinois Dept. of Revenue ST-23-0017-GIL (2023) (sales tax, advisory only)

Illinois generally excludes foreign affiliates and 80/20 companies—entities with 80% or more of their business activity outside the United States—from the unitary combined group for corporate income tax purposes, as defined at 35 ILCS 5/1501(a)(27). However, certain income or deductions involving these excluded entities may still factor into Illinois corporate income through statutory addback provisions and anti-abuse rules under Section 203.

Related-party expense addbacks (Schedule 80/20, Section 203 addbacks):

• Illinois requires a corporation to add back otherwise deductible interest and intangible expenses paid to related parties that are 80/20 companies or foreign affiliates, unless an express exception applies. Specifically, 35 ILCS 5/203(b)(2)(E-10) and (E-13) provide that a deduction is disallowed for interest or intangible expenses paid to "a person who would be a member of the same unitary business group if not for the application of item (iii) of subparagraph (A) of paragraph (27) of subsection (a) of Section 1501," i.e., an excluded 80/20 company. This is reported annually on Illinois Schedule 80/20 (lines 1–4), and the Schedule 80/20 instructions provide computation detail.

Corresponding subtraction for income received:

• When a corporation receives interest or intangible income from an affiliated 80/20 company or foreign affiliate, and a corresponding related expense has been added back on the payor’s Illinois return, the income recipient may subtract the corresponding amount, but only up to the related addition. This mechanism prevents double inclusion and is explained in Schedule 80/20, lines 5–6.

Anti-abuse authority (Section 203(f)):

• Under 35 ILCS 5/203(f), if the Department of Revenue "determines that any item of income, deduction, credit, or other amount should be reallocated, disallowed, or recomputed in order to prevent the avoidance of tax... and that avoidance was one of the principal purposes" of the arrangement, it may make such adjustments as necessary. Thus, the Department is authorized to disallow deductions, reallocate income, or require recharacterization if it finds a principal purpose of tax avoidance in transactions with foreign affiliates or 80/20 companies.
• Addback is not automatic solely because a payee is a foreign parent; the statutory addback rules and the anti-abuse test each contain specific factual thresholds.

Reporting for groups with foreign parents:

• Illinois law does not require inclusion of foreign parents’ income in the combined group but grants the Department authority to require documentation relevant to determining liability. 35 ILCS 5/506 authorizes the Department to require any books, papers, or information relevant to return accuracy and tax computation.

Annual compliance:

• Taxpayers with transactions involving excluded 80/20 companies or foreign affiliates must annually compute and report addbacks and corresponding subtractions using Illinois Schedule 80/20 for each tax year when such payments occur. The instructions, including line references for each step, are mandatory guidance for corporate filers.

Authority and references: Source: 35 ILCS 5/203(b)(2)(E-10), (E-13) Source: 35 ILCS 5/203(f) Source: 35 ILCS 5/1501(a)(27) Source: Illinois Schedule 80/20 Instructions Source: 35 ILCS 5/506