Illinois REG-1 Form: What It Is, Why It Matters, and How to File It

What Is the Illinois REG-1 Form?

  • The REG-1 is the official business registration form used by the Illinois Department of Revenue (IDOR).
  • It’s how businesses register to collect sales tax, pay employee withholding, and report other state taxes.

Why Businesses Need to File REG-1

  • Illinois law requires any business selling taxable goods or services, hiring employees, or leasing property in the state to register with the IDOR.
  • Filing ensures you’re set up to collect and remit the right taxes from day one—avoid penalties later.

Who Needs to File the REG-1?

  • Brick-and-mortar shops in Illinois.
  • Online sellers shipping to Illinois customers (economic nexus rules apply if you exceed $100K in sales or 200+ transactions in the state).
  • Remote businesses with employees or contractors located in Illinois.
  • Freelancers and consultants doing business under a trade name.
  • Landlords renting commercial property in Illinois.

What Taxes Does REG-1 Apply To?

  • Sales and Use Tax – If you sell physical products or certain digital goods.
  • Withholding Tax – If you have employees and need to withhold state income tax.
  • Telecommunications, Hotel Operators, Liquor, or Cannabis Tax – Industry-specific options appear during registration.
  • Use Tax – If you’re buying equipment or inventory out of state.

Step-by-Step: How to File the REG-1 Online

  • Step 1: Go to https://mytax.illinois.gov
  • Step 2: Click “Register a New Business” (you don’t need an account yet).
  • Step 3: Enter your EIN (or SSN for sole proprietors), legal business name, and DBA (if applicable).
  • Step 4: Provide your start date for sales, payroll, or business operations in Illinois.
  • Step 5: Choose which taxes you’ll be responsible for.
  • Step 6: Add info for each location where you operate in Illinois (even if remote).
  • Step 7: Review everything and hit submit—you’ll get a confirmation screen and a reference number.

After You Register

  • Within a few business days, the IDOR will mail you a Certificate of Registration and your Illinois Account ID.
  • You’ll also get instructions on how to start filing and paying taxes through MyTax Illinois.

Common Mistakes to Avoid

  • Picking the wrong tax types—read each section carefully and don’t over-register.
  • Skipping locations—each warehouse, store, or office in IL must be listed.
  • Using different names than your IRS documents—this creates processing delays.

Need to Register By Paper?

  • While online filing is fastest, you can also download and print the REG-1 PDF from the IDOR website.
  • Mail it to the address listed at the bottom of the form—but expect slower processing.

Where to File the REG-1

👉 MyTax Illinois: https://mytax.illinois.gov
👉 Paper version (PDF): REG-1 Form on IDOR site

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