Illinois Form ST-556, the Sales Tax Transaction Return, is the form every Illinois retailer must file when they sell a titled or registered item, such as a motor vehicle, watercraft, aircraft, trailer, or mobile home, to a buyer who will title or register the item in Illinois. The Illinois Department of Revenue (IDOR) uses this return to collect Retailers’ Occupation Tax (ROT) and the matching Use Tax on the buyer’s purchase, with the current revision dated R-12/23 available on the official IDOR ST-556 page.
Illinois dealers file more than 1.6 million ST-556 returns each year, and IDOR’s audit data shows roughly 1 in 8 paper returns contain a math, exemption, or local-tax error that triggers a notice. Filing the return wrong, late, or in the wrong channel costs dealers penalties, interest, and customer goodwill, because a buyer cannot get a clean Illinois title until the ST-556 clears.
Here is what this guide covers:
- 🧾 What ST-556 is, who must file it, and the 20-day clock that starts the moment you deliver the item
- 📋 Every document, ID number, and code you need before opening the return
- ✍️ A line-by-line walkthrough of every field, with sample entries and field-level traps
- 🚗 Three full filled-out examples for a car sale, a boat sale to a non-resident, and a family-member transfer
- ⚠️ The 12 most common mistakes that trigger IDOR notices, plus a Do/Don’t list and 14 FAQs
What Form ST-556 Is and Who Must File It
Form ST-556 is the Illinois return retailers use to report the sale of an item that must be titled or registered with a state agency, including the Illinois Secretary of State, the Illinois Department of Natural Resources, or the Federal Aviation Administration. The return is required by the Retailers’ Occupation Tax Act, 35 ILCS 120, and the matching Use Tax Act, 35 ILCS 105, with administrative rules in 86 Ill. Adm. Code 130.
Any Illinois-registered retailer who sells one of these covered items to a purchaser who will title or register it in Illinois must file ST-556. That includes franchised car dealers, used-car lots, RV dealers, marine dealers, aircraft dealers, trailer sellers, and mobile-home retailers. Out-of-state dealers who sell to Illinois residents are also required to file when the item will be titled in Illinois, under the Leveling the Playing Field for Illinois Retail Act guidance.
ST-556 is not used for leases of one year or longer; those go on Form ST-556-LSE. It is also not used for casual, person-to-person sales, which use Form RUT-50 (vehicles), RUT-75 (aircraft and watercraft), or RUT-25 (out-of-state purchases). The cousin returns are listed on the IDOR private-party transaction page.
The form is due within 20 days of the date of delivery to the purchaser. Missing that deadline triggers a late-filing penalty under 35 ILCS 735/3-3 of 2% of the tax due (capped at $250) for returns up to 30 days late, and a separate late-payment penalty that climbs from 2% to 15% based on how late the payment is. Interest accrues at the rate set by IDOR each year.
Before You Start: Documents and Information You Need
Open ST-556 only after you have everything in front of you, because the 20-day clock does not stop while you hunt for paperwork. The pre-filing checklist below covers every input the form asks for, plus the supporting records IDOR may request later in an audit.
- Your Illinois Business Tax (IBT) number. This is your account number with IDOR; without it, the return cannot post to your account, and the buyer’s title application will stall. Look it up in MyTax Illinois.
- The buyer’s full legal name and address. The address controls the local tax rate after the 2022 destination-sourcing rule change for vehicles described in IDOR Informational Bulletin FY 2022-15.
- The item’s identification number. That is the VIN for vehicles, the hull identification number (HIN) for boats, the N-number for aircraft, or the serial number for mobile homes; an error here voids the title application.
- Date of delivery. This is the date the buyer took possession, not the date the contract was signed; it starts the 20-day filing clock.
- Selling price and trade-in details. You need the gross selling price, the trade-in description, and the trade-in allowance, because the trade-in credit reduces the taxable base.
- Exemption code and supporting certificate. If the sale is exempt, you need the correct two-digit code from the ST-556 instructions and the matching certificate, such as a Form RUT-7 rolling-stock certificate or a drive-away permit.
- Bill of sale and odometer statement. Federal law and Illinois Secretary of State rules require an odometer disclosure for most vehicles under 20 years old.
- Manufacturer’s Statement of Origin (MSO) or prior title. The buyer’s title application travels with the ST-556, and the title chain must be clean.
- Lienholder information, if any. The lienholder name and address go on the title paperwork the buyer files with the Illinois Secretary of State.
- Your software vendor’s EDI credentials, if filing electronically. Most franchised dealers file ST-556 through approved DMS providers using IDOR’s electronic filing program described on the ST-556 electronic filing page.
Where to Get the Form and How to Access It
Unlike most Illinois tax forms, ST-556 is not a fillable PDF you can download and print. IDOR ships preprinted, transaction-numbered paper returns to registered dealers on request, and the electronic version is filed through approved third-party software or directly inside MyTax Illinois. The official ST-556 form page explains both options and lists the current revision date.
To order paper ST-556 returns, registered dealers call IDOR’s Central Registration Division at 217-785-3707 or submit a written request on dealership letterhead. IDOR mails the booklets in batches preprinted with your IBT number and a unique transaction number on each return; you cannot photocopy a blank form, because the transaction number is what links the return to the buyer’s title application.
To file electronically, you log into MyTax Illinois and either key the return directly into the ST-556 web application or upload a batch file produced by your dealership management system. IDOR maintains a list of approved ST-556 software vendors such as CDK, Reynolds and Reynolds, Dealertrack, and Tekion. Electronic filing is faster, posts the same day, and produces a confirmation number you can hand to the buyer.
If you sell only occasionally, such as a leasing company disposing of off-lease units, you may file a single ST-556 inside MyTax Illinois without ordering a booklet. Out-of-state dealers selling to Illinois residents register through MyTax Illinois first, then file the same way Illinois dealers do.
Step-by-Step: How to Fill Out Form ST-556 Line by Line
The walkthrough below follows the R-12/23 paper version of ST-556 in the same order the boxes appear on the return. The electronic version uses the same labels and box numbers, so the instructions translate directly. Italicized text shows what an actual entry looks like on the form.
Step 1, Line 1: Identify the Purchaser
This block asks for the buyer’s full legal name, street address, city, state, ZIP code, and county. Print the name exactly as it appears on the buyer’s driver’s license, because the Illinois Secretary of State cross-checks the title application against the ST-556. Use the buyer’s residence address for an individual and the registered business address for a company.
For example, Maria Lopez, 412 N. Ridgeway Ave., Chicago, IL 60624, Cook County is what a Chicago buyer’s block looks like.
If the buyer has only a P.O. Box, you must still enter a physical street address, because the local tax sourcing rule keys to the physical delivery address. A common mistake is using the buyer’s mailing address instead of the residence address, which sends the local tax to the wrong jurisdiction and triggers an IDOR adjustment notice that the dealer, not the buyer, must answer.
A misconception is that the buyer’s address only matters for mailing. In fact, after the 2022 destination-sourcing change, the buyer’s address sets the local Retailers’ Occupation Tax rate for most vehicle sales, which can swing the tax bill by hundreds of dollars.
Step 1, Line 2: Co-Purchaser
Enter the second buyer’s full legal name and address only if the title will be issued in two names. The form has space for one co-purchaser; for three or more buyers, you must attach a statement listing the additional names.
For example, Carlos Lopez, 412 N. Ridgeway Ave., Chicago, IL 60624 is the co-purchaser entry for Maria’s husband.
If the co-purchaser lives at a different address, use that address, because the Secretary of State will mail the title to the first listed buyer. A common mistake is leaving Line 2 blank when the buyer asked for joint title; that mismatch forces the buyer back to the dealership for a corrected ST-556-X.
The misconception is that adding a co-purchaser changes the tax. It does not, because the tax is on the gross selling price regardless of how many names appear on the title.
Step 2, Line 3: Describe the Item Sold
Enter the year, make, model, and identification number of the item. For a car or truck, that is the 17-digit VIN; for a boat, the HIN; for an aircraft, the FAA N-number and serial number; for a mobile home, the manufacturer’s serial number. Check each character twice, because a single transposed digit voids the title application.
For example, 2024 Toyota RAV4, VIN 2T3W1RFV5RW123456 is a typical car entry.
For a watercraft sale, also enter the length and the type of propulsion, because the Illinois Department of Natural Resources uses those fields for registration. A common mistake is entering the engine serial number instead of the HIN; the DNR will reject the registration, and the buyer cannot use the boat until the dealer files an amended return.
The misconception is that the VIN on the window sticker is always right. Always copy the VIN from the actual stamped plate or the MSO, because window-sticker VINs occasionally contain printing errors.
Step 3, Line 4: Selling Price, Trade-In, and Taxable Base
Line 4 is where most ST-556 errors happen, because it walks through the math that produces the taxable amount. Enter the gross selling price on Line 4a, the trade-in allowance on Line 4b, and subtract to get the taxable amount on Line 4c.
For example, $32,500.00 on Line 4a, $10,000.00 on Line 4b, and $22,500.00 on Line 4c is a clean entry for Maria Lopez trading in her old sedan.
For sales on or after January 1, 2022, the trade-in credit on first-division motor vehicles (most cars and light trucks) is uncapped again under Public Act 102-0700, after a brief period when it was capped at $10,000. A common mistake is still capping the trade-in at $10,000 out of habit, which overstates the tax and overcharges the buyer.
The misconception is that doc fees are not taxable. In Illinois, the documentary fee is part of the selling price and goes on Line 4a, not somewhere outside the tax base.
Step 4, Line 5: Was the Item Delivered Out of State?
Check this box only if you delivered the item to the buyer outside Illinois under a non-resident drive-away or fly-away exemption. If checked, attach the drive-away permit or non-resident certificate and use exemption code 23 in Step 5.
For example, Yes and Delivered to Hammond, Indiana on 03/14/2026 is what a non-resident sale looks like.
A common mistake is checking this box because the buyer lives out of state but actually took delivery on the dealer’s Illinois lot; that is still an Illinois-taxable sale, and IDOR will assess the full tax plus penalties on audit. The misconception is that the buyer’s out-of-state license alone proves out-of-state delivery; it does not, because delivery is a fact about where the keys changed hands, not where the buyer lives.
Step 5, Line 6: Exemption Code
If the sale is exempt or partially exempt, enter the two-digit code from the ST-556 instructions in Line 6. Common codes include 02 for sales to interstate carriers (rolling stock), 05 for sales to government bodies, 08 for organ-of-government, 17 for transfers to a beneficiary, and 23 for non-resident drive-away.
For example, 02 with a completed Form RUT-7 attached is the entry for a tractor sold to a federally licensed motor carrier.
A common mistake is using code 05 for a not-for-profit instead of code 08; the not-for-profit must hold a valid IDOR exemption identification “E-number,” and using the wrong code voids the exemption on audit. The misconception is that any non-profit qualifies; only those with an active E-number issued by IDOR’s Sales Tax Exemption Section qualify.
Step 6, Line 7: Tax Calculation
Line 7 multiplies the taxable amount on Line 4c by the combined state and local Retailers’ Occupation Tax rate. For most cars and light trucks delivered on or after July 1, 2022, the local rate is sourced to the buyer’s address, not the dealer’s address, per Illinois Public Act 101-0031 and IDOR’s destination-sourcing rules. Use the MyTax Illinois Tax Rate Finder to confirm the rate.
For example, $22,500.00 × 9.50% = $2,137.50 is the tax on Maria’s Chicago purchase.
A common mistake is using the dealer’s home rate for a buyer in a different town, which underpays or overpays the local share and triggers an IDOR notice months later. The misconception is that the state portion is always 6.25%; that is true for the state ROT, but the local add-ons (home-rule, RTA, county school facility) can push the combined rate above 11% in some Cook County addresses.
Step 7, Line 8: Credit for Tax Paid to Another State
If the buyer paid sales or use tax to another state on the same item, enter that amount on Line 8. The credit cannot exceed the Illinois tax due, and you must keep proof of the other state’s tax in your records.
For example, $1,200.00 with a copy of an Indiana ST-108 receipt attached is a typical entry for a relocating buyer.
A common mistake is granting the credit without documentation, which IDOR will disallow on audit. The misconception is that the credit applies to private-party purchases too; on ST-556, it only applies to retailer sales documented with another state’s official receipt.
Step 7, Line 9: Net Tax Due
Subtract Line 8 from Line 7 to get the net tax due. This is the dollar amount you remit with the return.
For example, $2,137.50 − $0.00 = $2,137.50 for Maria.
A common mistake is rounding to the nearest dollar; ST-556 requires entries to the cent. The misconception is that you can round up “to be safe”; over-collected tax must be either refunded to the buyer or remitted to IDOR, never pocketed.
Step 8, Line 10: Date of Delivery
Enter the date the buyer took physical possession in MM/DD/YYYY format. This date starts the 20-day filing clock and controls which tax rate applies if the rate changed between contract and delivery.
For example, 03/14/2026 is the delivery date for Maria’s RAV4.
A common mistake is using the contract date instead of the delivery date; if delivery happened a week later, the filing deadline is also a week later, but the wrong date can make a timely return look late. The misconception is that “delivery” means when financing funded; it means when the keys and item left the dealer’s control.
Step 9, Signature Block
The owner, partner, or authorized officer of the dealership must sign and date the return, print their title, and enter a daytime phone number. An unsigned ST-556 is treated as not filed.
For example, Janet Reyes, Title Clerk, 312-555-0144, 03/16/2026 is a typical signature line at a Chicago dealership.
A common mistake is letting an unauthorized employee sign; IDOR can reject the return and assess a late-filing penalty. The misconception is that an electronic ST-556 does not need a signature; the electronic submission carries the same authorization, and the filer’s MyTax Illinois credentials serve as the signature under 86 Ill. Adm. Code 760.
Three Filled-Out Examples Using Real Scenarios
Below are three full walkthroughs that show how the form looks for the most common ST-556 fact patterns. Each scenario follows one named buyer through every major box.
Scenario 1: Maria Lopez Buys a New Car With a Trade-In
Maria buys a 2024 Toyota RAV4 from a Chicago dealer for $32,500 and trades in her 2017 Camry valued at $10,000.
| Form Section | What the Dealer Enters for Maria |
|---|---|
| Line 1 Purchaser | Maria Lopez, 412 N. Ridgeway Ave., Chicago, IL 60624, Cook County |
| Line 2 Co-Purchaser | (blank) |
| Line 3 Item | 2024 Toyota RAV4, VIN 2T3W1RFV5RW123456 |
| Line 4a Selling Price | $32,500.00 |
| Line 4b Trade-In | $10,000.00 (2017 Toyota Camry, VIN 4T1BF1FK7HU123456) |
| Line 4c Taxable Amount | $22,500.00 |
| Line 6 Exemption Code | (blank, fully taxable) |
| Line 7 Tax (9.50%) | $2,137.50 |
| Line 10 Delivery Date | 03/14/2026 |
| Signature | Janet Reyes, Title Clerk, 03/16/2026 |
Scenario 2: David Chen, a Wisconsin Resident, Buys a Boat
David, a Milwaukee resident, buys a new pontoon boat from a Lake County, Illinois marine dealer for $48,000 and tows it home the same day under a non-resident drive-away.
| Form Section | What the Dealer Enters for David |
|---|---|
| Line 1 Purchaser | David Chen, 2210 N. Farwell Ave., Milwaukee, WI 53202 |
| Line 3 Item | 2026 Bennington 23RSB, HIN BEN12345J526, 23 ft, outboard |
| Line 4a Selling Price | $48,000.00 |
| Line 4b Trade-In | $0.00 |
| Line 4c Taxable Amount | $48,000.00 |
| Line 5 Out-of-State Delivery | Yes, delivered to Milwaukee, WI 03/22/2026 |
| Line 6 Exemption Code | 23 (non-resident) |
| Line 7 Tax | $0.00 (exempt) |
| Line 10 Delivery Date | 03/22/2026 |
| Attachment | Signed non-resident purchaser statement |
Scenario 3: Aisha Patel Buys an RV With a Rolling-Stock Exemption
Aisha owns an interstate moving company and buys a 2026 Freightliner box truck for $96,000 from a Joliet truck dealer, claiming the rolling-stock exemption.
| Form Section | What the Dealer Enters for Aisha |
|---|---|
| Line 1 Purchaser | Patel Moving LLC, 800 W. Cermak Rd., Chicago, IL 60608 |
| Line 3 Item | 2026 Freightliner M2 106, VIN 1FVACWDU8RHAA1234 |
| Line 4a Selling Price | $96,000.00 |
| Line 4b Trade-In | $0.00 |
| Line 4c Taxable Amount | $96,000.00 |
| Line 6 Exemption Code | 02 (rolling stock) |
| Line 7 Tax | $0.00 |
| Line 10 Delivery Date | 04/02/2026 |
| Attachment | Completed Form RUT-7 with USDOT number 3344556 |
| Signature | Mark O’Brien, General Manager, 04/03/2026 |
How to File the Completed Form
Illinois dealers can file ST-556 through three channels: electronically through MyTax Illinois, electronically through approved DMS software, or by mail on preprinted paper. IDOR strongly prefers electronic filing because it posts the same day and produces an immediate confirmation number for the buyer’s title application.
To file inside MyTax Illinois, log in at mytax.illinois.gov, choose the ST-556 tile, key in the return, attach any required certificates as PDFs, and pay by ACH debit, ACH credit, or credit card (a 2.25% processor fee applies to credit cards). Processing time is same-day, and the system emails a confirmation you should print and staple to the deal jacket.
To file through approved DMS software, your F&I clerk submits the return as part of the daily title batch, and the vendor transmits it to IDOR using the ST-556 EDI specifications. Payment is by ACH debit pulled from the dealership’s operating account. Processing is same-day, and confirmations come back inside the DMS within minutes.
To file by mail, mail the white copy of the preprinted return with a check payable to Illinois Department of Revenue to Illinois Department of Revenue, P.O. Box 19034, Springfield, IL 62794-9034. There is no separate filing fee, only the tax due. Processing takes 4 to 6 weeks, and your proof of filing is the certified-mail receipt plus the dealer’s pink copy of the preprinted return; keep both for at least 3.5 years under the retention rule in 86 Ill. Adm. Code 130.815.
The buyer’s title application travels separately to the Illinois Secretary of State Vehicle Services Department at 501 S. Second St., Springfield, IL 62756, with a copy of the ST-556 confirmation as proof the tax was paid.
What Happens After You File
Once IDOR accepts the ST-556, the system posts the tax to your IBT account, releases a clearance to the Illinois Secretary of State (or DNR or FAA), and sends you a confirmation. The buyer’s title is then issued in 6 to 8 weeks for paper filings or 2 to 4 weeks for electronic filings, per the Secretary of State title processing schedule.
If IDOR finds a math error, an exemption-code mismatch, or a local-rate problem, it mails a Form CRN-1 notice to the dealer (not the buyer) explaining the adjustment and any tax, penalty, or interest due. You have 60 days to pay or to protest the notice in writing under 86 Ill. Adm. Code 200.
If you discover your own error after filing, file Form ST-556-X to amend the return; the ST-556-X form and instructions are on the IDOR site. Common amendments correct a wrong VIN, a missed trade-in credit, or a buyer-address change.
If the buyer cancels the deal before titling, file ST-556-X marked “rescinded sale” and refund the tax to the buyer. IDOR then credits your account once the amended return posts.
Mistakes to Avoid When Filling Out the Form
- Using the dealer’s address for local tax instead of the buyer’s address, which underpays or overpays local ROT and triggers a CRN-1 adjustment.
- Capping the trade-in at $10,000 out of habit on first-division vehicles, which overstates tax and forces a refund through ST-556-X.
- Transposing a digit in the VIN or HIN, which voids the title application and forces the dealer to refile.
- Using the contract date as the delivery date, which can make a timely return look late and trigger a late-filing penalty.
- Leaving the exemption code blank when claiming exempt status, which IDOR treats as a fully taxable sale on audit.
- Using exemption code 05 for a not-for-profit without an active E-number, which voids the exemption and assesses tax plus interest.
- Forgetting to attach RUT-7 for a rolling-stock claim, which IDOR disallows even if the buyer truly qualifies.
- Granting another-state credit without proof, which IDOR removes on audit and bills back to the dealer.
- Photocopying a blank ST-556, which lacks a transaction number and is rejected by IDOR’s mailroom.
- Letting an unauthorized employee sign the return, which IDOR may treat as an unfiled return.
- Pocketing over-collected tax, which violates 35 ILCS 120/2-40 and exposes the dealer to civil and criminal penalties.
- Missing the 20-day deadline, which adds a 2% late-filing penalty and 2% to 15% late-payment penalty plus daily interest.
Do’s and Don’ts
- Do confirm the buyer’s address on a government-issued ID, because the local tax rate keys to that address.
- Do verify the VIN or HIN against the stamped plate, not just the paperwork, because printing errors are common.
- Do file electronically when possible, because same-day posting speeds the buyer’s title.
- Do keep a complete deal jacket for 3.5 years, because that is the IDOR retention period.
- Do train every F&I clerk on exemption codes, because misuse is the top audit issue.
- Do call IDOR at 217-785-3707 when in doubt, because a 5-minute call beats a 6-month audit.
- Don’t use a P.O. Box as the buyer’s address on Line 1, because sourcing rules require a physical location.
- Don’t subtract the trade-in twice (once on Line 4b and again on Line 7), because the math built into Line 4c already does it.
- Don’t mail the dealer’s pink copy to IDOR; mail the white copy and keep the pink copy for your records.
- Don’t assume an out-of-state buyer is automatically exempt, because delivery on Illinois soil is taxable regardless of residency.
- Don’t wait to file until the buyer’s check clears; the 20-day clock runs from delivery, not funding.
- Don’t discard exemption certificates after filing, because IDOR can request them for up to 3.5 years.
Pros and Cons of Filing on Your Own vs. With Help
- Pro of self-filing: No outside fees, because MyTax Illinois is free.
- Pro of self-filing: Full control of timing, because you file the moment the deal closes.
- Pro of self-filing: Direct visibility into IDOR notices, because they come straight to you.
- Pro of self-filing: Faster customer experience, because the buyer leaves with a confirmation number in hand.
- Pro of self-filing: Builds in-house expertise, which pays off across hundreds of deals a year.
- Con of self-filing: Steep learning curve on exemption codes, which is the top audit issue.
- Con of self-filing: Time cost on busy weekends, when title clerks juggle dozens of deals.
- Con of self-filing: Risk of math errors that an outside service would catch, which leads to ST-556-X amendments.
- Con of self-filing: No safety net for unusual fact patterns, such as multi-state interstate carriers.
- Con of self-filing: Personal liability for the signer, who is on the hook if IDOR finds fraud.
ST-556 vs. ST-556-LSE at a Glance
| Topic | ST-556 (Sales) vs. ST-556-LSE (Leases of 1+ year) |
|---|---|
| Triggering transaction | Outright sale of titled item vs. lease of one year or longer |
| Tax base | Gross selling price minus trade-in vs. total of lease payments plus down payment |
| Filing deadline | Within 20 days of delivery vs. within 20 days of lease start |
| Trade-in credit | Allowed and uncapped on first-division vehicles vs. allowed only on like-kind item turned in by lessee |
| Form source | ST-556 page vs. ST-556-LSE page |
FAQs
Is ST-556 the right form for a private sale between two neighbors?
No. ST-556 is only for Illinois-registered retailers. A private-party vehicle sale uses Form RUT-50; a private-party watercraft or aircraft sale uses Form RUT-75.
Do I file ST-556 if I sell to an out-of-state dealer for resale?
No. A documented sale for resale is exempt; collect the buyer’s resale certificate and use exemption code 01, but you still file the ST-556 showing the exempt sale.
Can I file ST-556 after the 20-day deadline without a penalty?
No. The late-filing penalty starts the day after the deadline, but if the tax is paid on time, the late-payment penalty is avoided.
Should I list the buyer’s mailing address or residence address on Line 1?
No mailing addresses; use the residence or registered business address, because local tax sourcing keys to the physical location.
Do I include the documentary fee in the selling price on Line 4a?
Yes. The Illinois doc fee is part of the gross selling price and is fully taxable on Line 4a.
Is the trade-in credit still capped at $10,000 on first-division vehicles?
No. The cap was removed for sales on or after January 1, 2022, by Public Act 102-0700, so first-division vehicle trade-ins are uncapped again.
Can I correct a wrong VIN by writing over it on the paper return?
No. File Form ST-556-X to correct the VIN, because IDOR’s scanner reads the original entry and a write-over voids the return.
Is the buyer’s signature required on ST-556?
No. Only the dealer’s authorized signer must sign; the buyer signs the bill of sale and the title application instead.
Should I check the out-of-state delivery box if the buyer drove home to Indiana the same day?
No unless you actually delivered the item across the state line; same-day departure from the Illinois lot is still an Illinois-taxable delivery.
Can I claim a tax credit for sales tax the buyer paid in another state?
Yes. Enter the documented amount on Line 8, but the credit cannot exceed the Illinois tax due on Line 7.
Is an electronic ST-556 legally equivalent to a paper one?
Yes. A MyTax Illinois submission carries the same legal weight under 86 Ill. Adm. Code 760, with the user’s credentials serving as the signature.
Do I need to keep the exemption certificate after IDOR accepts the return?
Yes. Keep all exemption certificates for at least 3.5 years, because IDOR can request them on audit and disallow the exemption without them.
Can a leasing company file a single ST-556 without ordering a booklet?
Yes. Occasional filers can submit one-off ST-556 returns directly inside MyTax Illinois without preprinted forms.
Is the dealer or the buyer responsible if the local tax rate is wrong?
No to buyer responsibility; the dealer is the taxpayer of record on ST-556 and absorbs any IDOR adjustment, even when the buyer supplied the wrong address.
Related reading
- How to Fill Out Illinois Form IL-1120-ST (w/Examples) + FAQs
- How to Fill Out Illinois Form ST-1 (w/Examples) + FAQs
- How to Fill Out Illinois Form ST-1-X (w/Examples) + FAQs
- How to Fill Out Illinois Form ST-44 (w/Examples) + FAQs
- How to Fill Out Illinois Form ST-587 (w/Examples) + FAQs
- How to Fill Out Illinois Securities Notice of Sales Pursuant to Rule 130 + FAQs