The Oakbrook Terrace sales tax on general merchandise is 9.00%, combining Illinois state tax, a regional transit levy, DuPage County’s share, and the city’s home rule tax. Groceries, prescription drugs, and certain medical items are taxed at lower rates, and titled purchases like vehicles follow a separate destination-based rule.
What Makes Up the 9.00% Rate
Four taxing authorities contribute to the rate a customer pays at the register:
- State of Illinois: 6.25%, imposed under the Retailers’ Occupation Tax Act.
- Regional Transportation Authority: 1.00%, applied throughout the six-county RTA region, which includes DuPage County.
- DuPage County: 0.25%.
- City of Oakbrook Terrace: 1.50%, a home rule municipal tax the city can set without a voter referendum.
The total is charged as a single line at the point of sale. The Illinois Department of Revenue collects the full amount and distributes the local portions back to the county and city. You can verify the current combined rate for any specific address using the Tax Rate Finder inside MyTax Illinois.1Illinois Department of Revenue. Sales Tax and Use Tax
Groceries After January 2026
Illinois eliminated its 1% state-level sales tax on grocery food effective January 1, 2026. In its place, municipalities and counties can adopt a local grocery tax of exactly 1% by ordinance, without a referendum, and more than half of Illinois municipalities have done so. The RTA tax on grocery food also continues to apply in the RTA region, which includes Oakbrook Terrace.2Illinois Department of Revenue. FY 2026-11, Municipal and County Grocery Occupation Tax Rate
Groceries for this purpose means food for human consumption that will be eaten off the premises where it’s sold. Several categories are excluded and taxed at the full 9.00% general merchandise rate:
- Prepared food ready for immediate consumption, such as hot meals, deli sandwiches, and salad bar items.
- Soft drinks and candy.
- Alcoholic beverages.
- Food infused with adult-use cannabis.
The prepared-food line catches shoppers most often. A rotisserie chicken from the deli case is taxed at the full rate; a raw chicken from the meat department is a grocery item.3Illinois Department of Revenue. Illinois Grocery Tax Changes Effective January 1, 2026
Prescriptions and Medical Items
Prescription and nonprescription medicines, medical appliances, insulin, and diabetic supplies are taxed at a 1% state rate rather than 6.25%. This reduced rate is separate from the grocery changes and remains in effect for 2026.4Legal Information Institute. Illinois Code Title 86, 140.126 – Taxation of Food, Drugs and Medical Appliances
Buying a Vehicle
Cars, trucks, motorcycles, ATVs, and other titled items follow a different tax structure than ordinary retail goods. The rate is determined by the purchaser’s home address, not the dealership’s location. Several use taxes, including the RTA use tax and any applicable home rule use tax, are triggered based on the address on Form ST-556. Shopping at a dealer in a lower-tax city won’t reduce what you owe.5Illinois Department of Revenue. Illinois Tax Requirements for Cars, Trucks, Vans, Motorcycles, ATVs, Trailers, and Mobile Homes
Use Tax on Out-of-State Purchases
When you buy from a retailer that doesn’t collect Illinois tax, you owe Illinois use tax on the purchase. The rate mirrors the sales tax structure: 6.25% on general merchandise and 1% on qualifying food, drugs, and medical appliances. If you paid sales tax to another state on the same item, Illinois credits that amount, and you owe only the difference when the other state’s rate was lower.6Illinois Department of Revenue. Use Tax Rates
Filing and Paying as a Business
Retailers file through MyTax Illinois using Form ST-1, Sales and Use Tax and E911 Surcharge Return. Before filing, you need to register your business and obtain an Illinois Business Tax number through the same portal.
The Department assigns your filing frequency based on how much tax you collect:
- Monthly if your average monthly tax liability is greater than $200.
- Quarterly if it’s between $50 and $200.
- Annual if it’s under $50.
Returns and payments are due by the 20th of the month following the end of your reporting period. If the 20th falls on a weekend or holiday, the deadline shifts to the next business day.7Illinois Department of Revenue. ST-1 Instructions – Sales and Use Tax and E911 Surcharge Return
Your return needs accurate records of gross receipts, the total value of any exempt sales such as sales for resale, and a clear separation between general merchandise and food, drugs, or medical items. Sales made within Oakbrook Terrace must be distinguished from sales in other jurisdictions so the correct local rates are applied.
The Timely Filing Discount
Retailers who file on time and pay electronically get a discount of 1.75% of the tax collected. For returns due on or after January 1, 2025, the discount is capped at $1,000 per month across all sales and use tax returns combined. You must file through MyTax Illinois to qualify, and missing the deadline forfeits the discount entirely.8Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 120/3
Late Filing and Late Payment Penalties
The late-filing penalty starts at 2% of the tax due, capped at $250. If you still haven’t filed within 30 days after the Department mails you a nonfiling notice, an additional penalty applies equal to the greater of $250 or 2% of the tax shown on the return, up to $5,000.9Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 735 – Uniform Penalty and Interest Act
Late-payment penalties are separate and steeper:
- Paid within 30 days of the due date: 2% of the unpaid amount.
- Paid more than 30 days late but before an audit begins: 10% of the unpaid amount.
- Paid after the Department initiates an audit: 20% of the unpaid amount, dropping to 15% if you pay everything within 30 days of receiving the amended return.
The jump from 2% to 10% after 30 days is where businesses get hurt. Paying something before that 30-day mark, even if you can’t pay in full, holds the penalty at the lower tier.
Recordkeeping
Keep records supporting every return for three and a half years after filing the original or amended return. If the Department has issued a Notice of Tax Liability, hold the records for that period until the liability is resolved.10Illinois Department of Revenue. Pub-113, Keeping Complete and Accurate Records During an audit, the Department reviews how you calculated the tax base, verifies exemptions and deductions, and tests returns against source documents and ledger accounts. Failing to produce requested records can result in a penalty of up to $3,000 per filing period.11Illinois Department of Revenue. Illinois Audit Information
Selling Into Oakbrook Terrace From Out of State
Physical presence isn’t required to trigger a collection obligation. As of January 1, 2026, a remote seller must collect and remit Illinois sales tax once cumulative gross receipts from Illinois sales reach $100,000 or more during the preceding 12-month period. The prior 200-transaction threshold has been eliminated.12Illinois Department of Revenue. FY 2026-12, Destination-Based Retailers Occupation Tax Changes Remote sellers check quarterly against lookback periods ending on the last day of March, June, September, and December, and begin collecting on the first day of the next quarter after crossing the threshold.
Marketplace facilitators like Amazon, eBay, and Etsy carry a separate obligation: the platform itself collects and remits sales tax on transactions made through the marketplace and is treated as the retailer for tax purposes on those sales. Sellers who also sell through their own websites or physical locations remain responsible for collecting tax on those non-marketplace transactions.13Illinois General Assembly. Illinois Compiled Statutes 35 ILCS 110/2d