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Avoid Common Filing Mistakes for Sales and Other Related Taxes

Filing electronically is the best way to avoid common, and sometimes costly, mistakes. Most sales and other related tax forms can be filed for free using MyTax Illinois. Once you submit your return electronically, do not mail a copy.

Use the following information to assist you in avoiding processing delays and applying for credit faster.

If you are filing on paper, use a calculator. Review the entries you made on each line for accuracy and verify your calculations.

File and pay based on the frequency the Department has assigned you.
Doing otherwise may lead to penalties for unfiled returns or late payments. If you had no activity for the filing period, or if no tax is due, you still must file a return reporting this.

Make sure you use the correct version of the form you are filing.
Forms are updated to comply with new laws or to improve taxpayer understanding. Each time an update is made, a new revision date is put on the form. This date is shown in parentheses, typically at the bottom of the form. Example: a form updated in April 2014 would show (R-04/14). The most current version of all forms is available for download at our website,

Vehicle, watercraft, and aircraft returns

(includes ST-556, ST-556-LSE, RUT-25, RUT-25-LSE, RUT-50, and RUT-75)

Do not make copies of your return to use for multiple transactions.
All vehicle, watercraft, and aircraft returns have a unique identifying number (Transaction, MV, PV, AV, or AW number) at the top that should not be duplicated.

When filing an amended return, you must include the unique identifying number (Transaction, MV, PV, AV, or AW number) from the original return that you are changing or correcting.

Complete all date fields with the required entry.

If you leave date fields blank or enter an invalid date, your return may be delayed and may lead to bills or correspondence requiring you to pay or to provide the correct information.

Provide all the required information on the return.

Other sales and related tax returns

(includes ART-1, CMFT-1, PST-1, ST-1, ST-4, ST-8, and ST-14)

Submit only one original return per reporting period.
If you file electronically or if your preparer files the return for you, do not mail a second copy of your return. Sending us multiple returns for a single reporting period causes unnecessary delays in the processing of your return.

When using MyTax Illinois to file your return, make sure you submit the return.
The “Save” feature does not send your return to the Department. If you are finished with your return and you are ready to send it to the Department, you must click the “Submit” button and provide your password as your signature. A confirmation page will appear verifying that your return has been submitted. The easiest way to make a payment for this return is from the confirmation screen. Click on the “Proceed to payment” button at the top of the confirmation screen to complete the payment process.

Fairs, festivals, flea markets, craft shows, antique malls and other similar venues may require special reporting of Form ST-1.
Make sure you know your reporting and payment requirements if you sell items at special events. PIO-28 at is a good resource to reference for these situations.

Businesses registered to file and pay using Form ST-1 must include any use tax liability they may owe as part of their filing.
Form ST-44 is for individuals and businesses that are not required to be registered to file Form ST-1.

Verify all payments before submitting.

Verify the tax rate that you are using.