Illinois Sales Tax Due Dates and Filing Requirements

In Illinois, businesses that sell tangible personal property at retail are responsible for collecting and remitting the state’s Retailers’ Occupation Tax, commonly known as sales tax. The Illinois Department of Revenue (IDOR) oversees the administration of this tax and establishes the deadlines and frequencies for all retailers. Understanding the specific rules for when and how to file is a primary compliance responsibility for every retailer operating within the state.

Determining Your Sales Tax Filing Frequency

The frequency with which a business must file its sales tax return is determined by its average monthly sales tax liability. The IDOR assigns a filing status to each business upon registration based on specific monetary thresholds. Retailers with an average monthly sales tax liability of less than $50 are permitted to file on an annual basis.

Businesses that collect between $50 and $200 per month in sales tax are assigned a quarterly filing status. The most common frequency is monthly, which is required for businesses collecting more than $200 in sales tax per month. The IDOR periodically reviews a business’s account and will issue a notification if a change in filing frequency is required due to shifts in sales volume.

Standard Due Dates for Filers

The deadline for filing a sales tax return and paying the tax owed is the 20th day of the month immediately following the end of the reporting period. This standard due date applies to annual, quarterly, and monthly filers, who use Form ST-1, Sales and Use Tax and E911 Surcharge Return. For a monthly filer, tax collected during January must be paid by February 20th.

A quarterly filer completing the first quarter must submit its return and payment by April 20th. For an annual filer, the entire tax liability for the previous calendar year is due on January 20th. If the 20th falls on a weekend or a state-recognized holiday, the deadline is extended to the next business day.

Accelerated Payment Requirements

Businesses with an average monthly sales tax liability of $20,000 or more are subject to an accelerated payment schedule. These “quarter-monthly” payers must remit payments more frequently than standard filers. They are required to make four payments during the month, with due dates on the 7th, 15th, 22nd, and the last day of the month.

Each payment is an estimate of the tax collected during the respective period. Despite these frequent payments, a reconciling return on Form ST-1 is still required. This final return must be filed by the standard 20th-of-the-month deadline to balance the prepayments made against the actual liability.

Penalties for Missing a Due Date

Failing to meet sales tax deadlines in Illinois results in the automatic assessment of financial penalties. The state imposes separate penalties for failing to file a return on time and for failing to pay the tax owed by the due date. The penalty for filing a return late is the lesser of $250 or 2 percent of the tax that was required to be shown on the return.

The penalty for paying late is 2 percent of the tax due if the payment is 1 to 30 days late, and 10 percent if it is more than 30 days late. In addition to these penalties, interest accrues on any unpaid tax from the day after the due date until the liability is paid in full.