Illinois Sales Tax return (Form ST-1) for self-employed individuals. Covers all four Illinois occupation and use taxes (ROT, UT, SOT, SUT), state and local rates, origin-based sourcing, vendor discount, and filing frequencies. Primary source: 35 ILCS 120/ (ROT), 35 ILCS 105/ (UT), 35 ILCS 115/ (SOT), 35 ILCS 110/ (SUT).
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ROT rate — general merchandise
6.25% state (general merchandise)35 ILCS 120/2-10; IDOR PIO-101.
ROT rate — qualifying food/drugs/medical
1.0% state rate for qualifying food/drugs/medical in 2025; the statewide 1% grocery tax is eliminated effective 1/1/2026 (localities may re-impose).35 ILCS 120/2-10; IDOR PIO-115; PA 103-0781.
SOT rate — general
6.25%35 ILCS 110/3-10.
SOT rate — general
6.25%35 ILCS 110/3-10.
SOT rate — general
6.25%35 ILCS 110/3-10.
SOT tax base
General SOT base = selling price of TPP transferred (if separately stated) or 50% of the entire bill if not separately stated; never less than cost. 'Cost price' applies only to de minimis servicepersons (cost-of-TPP < 35%, or < 75% pharmacy/graphic arts).86 Ill. Admin. Code 140.106; IDOR Pub-113.
Chicago — general
10.25% combined (state 6.25 + county/RTA/city)IDOR MyTax IL Rate Finder.
Springfield — general
Springfield combined rate is ~9.75% (6.25 state + 1.00 county + 2.50 city/home-rule); 8.75% is outdated. Confirm exact rate via MyTax IL Rate Finder.
Reviewed against the cited tax authorities by a licensed accountant on 2026-06-03.
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Obligation category: CT (Consumption Tax) Functional role: Return preparation Status: Complete
This is a Tier 2 content skill for preparing the Illinois Form ST-1 (Sales and Use Tax and E911 Surcharge Return). Illinois has a unique four-tax structure for sales/use taxes, and this skill covers all four taxes as they appear on the combined ST-1 return.
In scope:
Out of scope (refused):
Filing frequency (86 Ill. Admin. Code 130.601)
| Monthly tax liability | Filing frequency | Source |
|---|---|---|
| $200 or more/month (average) | Monthly (due 20th of following month) | 86 Ill. Admin. Code 130.601 |
| Less than $200/month (average) | Quarterly (due 20th after quarter end) | 86 Ill. Admin. Code 130.601 |
| Less than $50/month (average) | Annual (due January 20) | 86 Ill. Admin. Code 130.601 |
The four-tax structure (35 ILCS 120/2; 35 ILCS 105/3; 35 ILCS 115/3; 35 ILCS 110/3)
| Tax | Who pays | Rate (general merchandise) | Rate (qualifying food/drugs/medical) | Source |
|---|---|---|---|---|
| Retailers' Occupation Tax (ROT) | Seller | 6.25% state | 1.0% state | 35 ILCS 120/2 |
| Use Tax (UT) | Buyer (out-of-state) | 6.25% state | 1.0% state | 35 ILCS 105/3 |
| Service Occupation Tax (SOT) | Serviceperson | 6.25% state | 1.0% state | 35 ILCS 115/3 |
| Service Use Tax (SUT) | Consumer of service | 6.25% state | 1.0% state | 35 ILCS 110/3 |
Note: In practice, sellers collect all four taxes as a combined "sales tax" and remit on Form ST-1. The buyer sees a single tax rate.
State rate components (35 ILCS 120/2; 35 ILCS 120/2-10)
| Component | Rate | Source |
|---|---|---|
| State (general merchandise) | 6.25% | 35 ILCS 120/2 |
| State (qualifying food, drugs, medical appliances) | 1.00% | 35 ILCS 120/2-10 |
Illinois is origin-based for most transactions. The rate is determined by the seller's location.
Local rate add-ons (examples, 2025) (IDOR tax rate finder)
| Location | Combined rate (general) | Combined rate (food/drugs) | Source |
|---|---|---|---|
| Chicago | 10.25% | 2.25% | IDOR tax rate finder |
| Cook County (outside Chicago) | ~9.00-10.25% | varies | IDOR tax rate finder |
| Springfield (Sangamon Co.) | 8.75% | 2.00% | IDOR tax rate finder |
| Champaign | 9.00% | 2.00% | IDOR tax rate finder |
Important: Local rates vary by municipality and county. Always verify the exact combined rate for the seller's business location using the IDOR tax rate database (tax.illinois.gov).
Vendor discount (35 ILCS 120/3)
| Item | Amount | Source |
|---|---|---|
| Vendor discount | 1.75% of state tax collected and timely remitted | 35 ILCS 120/3 |
The vendor discount compensates the retailer for collecting and remitting tax. It applies only to the state portion of the tax and only if the return is filed and paid on time.
Input: Chicago seller. Gross sales: $20,000, all general merchandise, all in-store. No exempt sales. Expected: Combined rate: 10.25%. Tax: $20,000 x 10.25% = $2,050. State portion: $20,000 x 6.25% = $1,250. Vendor discount: $1,250 x 1.75% = $21.88. Net tax: $2,050 - $21.88 = $2,028.12.
Input: Springfield seller. General merchandise: $10,000. Qualifying food: $5,000. Expected: General: $10,000 x 8.75% = $875. Food: $5,000 x 2.00% = $100. Total: $975. State portion: ($10,000 x 6.25%) + ($5,000 x 1%) = $625 + $50 = $675. Vendor discount: $675 x 1.75% = $11.81. Net: $963.19.
Input: HVAC contractor in Champaign. Service charges: $3,000. Parts (cost price): $800. Expected: SOT applies to $800 (cost price of parts). Tax: $800 x 9.00% = $72.
Input: Chicago business purchases $5,000 of equipment from out-of-state vendor, no tax collected. Expected: Use tax: $5,000 x 10.25% = $512.50.
Input: Same as Test 1 but filed 10 days late. Expected: No vendor discount. Net tax: $2,050 plus penalties and interest.
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Review status
Accountant-reviewed
Reviewed by a named licensed practitioner against the stated sources, as general reference material.
Other Illinois computations in the OpenAccountants Tax Library.
Champaign — general
Component math supports 9.00% (6.25 + 1.25 county + 1.50 city); some third-party sources show 9.25% after recent local changes. Confirm via MyTax IL Rate Finder.IDOR MyTax IL Rate Finder.
Monthly tier
Monthly filers (avg > $200/mo tax) file ST-1 by the 20th of the following month86 Ill. Admin. Code 130.502; ST-1 instr.
Quarterly tier
Quarterly if avg <= $200/mo; due the 20th after quarter endST-1 instr.
Annual tier
Annual if avg < $50/mo; due January 20ST-1 instr.
Vendor discount rate
1.75% of tax timely remitted (min $5/yr); capped at $1,000/month effective 1/1/202535 ILCS 120/3; PA 103-0592; ST-1 instr.
Applies to
The discount is computed on TOTAL ST-1 tax due (Line 9, which includes locally imposed ROT), not the state portion only. ST-1 Step 4 applies 1.75% to Line 9, subject to the $1,000/month cap.ST-1 instr. (R-01/26), Step 4; 35 ILCS 120/3.
Late filing
Discount forfeited if the return is filed or tax paid late35 ILCS 120/3; IDOR guidance.
Sourcing
IL sourcing is hybrid, not purely origin-based. In-state retailers shipping from IL inventory use origin; remote retailers and marketplace facilitators meeting $100,000/200-transaction nexus source to destination; effective 1/1/2026 IL expands destination-based ROT for in-state sellers shipping from out of state.IDOR Pub-113; FY 2026-12; Leveling the Playing Field Act.
Qualifying food
Qualifying food excludes prepared food, candy, soft drinks, and alcohol (general rate)86 Ill. Admin. Code 130.310; IDOR PIO-115.
E-filing
IL generally mandates electronic ST-1 filing for most retailers (waiver via Form IL-900-EW). The $200 figure is the monthly-vs-quarterly filing-frequency threshold, not an e-file trigger.ST-1 instr.; 86 Ill. Admin. Code 130.
Registration requirement
Any person engaged in the business of selling tangible personal property at retail in Illinois must register with the Illinois Department of Revenue (IDOR) and collect and remit ROT. Servicepersons who transfer tangible personal property incident to a service must also register.35 ILCS 120/2.
Filing frequency
| Monthly tax liability | Filing frequency | Source | |----------------------|------------------|--------| | $200 or more/month (average) | Monthly (due 20th of following month) | 86 Ill. Admin. Code 130.601 | | Less than $200/month (average) | Quarterly (due 20th after quarter end) | 86 Ill. Admin. Code 130.601 | | Less than $50/month (average) | Annual (due January 20) | 86 Ill. Admin. Code 130.601 |86 Ill. Admin. Code 130.601
Electronic filing
Required for all taxpayers whose average monthly liability is $200 or more.35 ILCS 120/3.
The four-tax structure
| Tax | Who pays | Rate (general merchandise) | Rate (qualifying food/drugs/medical) | Source | |-----|----------|---------------------------|--------------------------------------|--------| | Retailers' Occupation Tax (ROT) | Seller | 6.25% state | 1.0% state | 35 ILCS 120/2 | | Use Tax (UT) | Buyer (out-of-state) | 6.25% state | 1.0% state | 35 ILCS 105/3 | | Service Occupation Tax (SOT) | Serviceperson | 6.25% state | 1.0% state | 35 ILCS 115/3 | | Service Use Tax (SUT) | Consumer of service | 6.25% state | 1.0% state | 35 ILCS 110/3 |35 ILCS 120/2; 35 ILCS 105/3; 35 ILCS 115/3; 35 ILCS 110/3
State rate components
| Component | Rate | Source | |-----------|------|--------| | State (general merchandise) | 6.25% | 35 ILCS 120/2 | | State (qualifying food, drugs, medical appliances) | 1.00% | 35 ILCS 120/2-10 |35 ILCS 120/2; 35 ILCS 120/2-10
Local rate add-ons (examples, 2025)
| Location | Combined rate (general) | Combined rate (food/drugs) | Source | |----------|------------------------|---------------------------|--------| | Chicago | 10.25% | 2.25% | IDOR tax rate finder | | Cook County (outside Chicago) | ~9.00-10.25% | varies | IDOR tax rate finder | | Springfield (Sangamon Co.) | 8.75% | 2.00% | IDOR tax rate finder | | Champaign | 9.00% | 2.00% | IDOR tax rate finder |IDOR tax rate finder
Vendor discount
| Item | Amount | Source | |------|--------|--------| | Vendor discount | 1.75% of state tax collected and timely remitted | 35 ILCS 120/3 |35 ILCS 120/3
Step 1
Selling tangible personal property at retail? --> ROT Providing a service that involves transferring tangible personal property? --> SOT Purchasing from out-of-state for own use in Illinois? --> UT/SUT Most small retailers will report primarily under ROT.
Step 2
For each sale, determine: 1. **Taxable or exempt?** (See Section 5 for exemptions.) 2. **General merchandise or qualifying food/drugs/medical?** (Determines rate.) 3. **Location of seller.** (Illinois is origin-based; the rate depends on WHERE YOU SELL FROM.)
Step 3
Sum all receipts from taxable and exempt sales.
Step 4
Deduct sales for resale, sales to exempt organizations, and other exempt transactions.
Step 5
General merchandise taxable receipts x applicable combined rate (state + local). Qualifying food/drug/medical taxable receipts x applicable combined rate (state + local at reduced rate).
Step 6
Sum of all tax amounts by rate category.
Step 7
If filing on time: - State tax portion x 1.75% = vendor discount. - The discount applies only to the state component, not local taxes.
Step 8
For items purchased from out-of-state vendors without IL tax collected, report use tax at the applicable rate.
Step 9
Total tax - vendor discount + use tax = net tax due.
Origin-based sourcing
Illinois is an origin-based state for most sales. The tax rate is determined by the location of the seller, not the buyer. Exception: sales by Illinois retailers to out-of-state buyers may be exempt (see E-3).86 Ill. Admin. Code 130.410.
Qualifying food, drugs, medical appliances
These items are taxed at the reduced 1% state rate (plus reduced local rates). Qualifying food includes most grocery items but NOT prepared food, soft drinks, candy, or alcoholic beverages.35 ILCS 120/2-10.
Interstate sales
Sales shipped to buyers outside Illinois are generally exempt from Illinois ROT if the seller ships the goods via common carrier or U.S. mail. The seller must retain proof of out-of-state delivery.35 ILCS 120/1.
Service vs. sale distinction
If a serviceperson transfers tangible personal property incident to a service, SOT applies to the cost price of the property transferred (not the full service charge). For example, a plumber who installs a faucet pays SOT on the faucet's cost price, not the labor charge.35 ILCS 115/3.
Exempt organizations
Sales to organizations holding a valid Illinois exemption identification number (E-number) are exempt. The seller must retain a copy of the exemption certificate.35 ILCS 120/2-5(11).
Zero returns
Retailers with no activity must still file a return showing zero tax. Failure to file results in penalties and potential revocation of the certificate of registration.
Prepaid calling arrangements
Prepaid calling arrangements are taxable as general merchandise at the point of sale.35 ILCS 120/2-25.
Rendered from the canonical facts model · method attested Jun 3, 2026 (covers the method, not the currency of individual figures). General reference only — confirm with a qualified professional before acting.
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