When is Form ST-1-X due?

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Form ST-1-X must be filed when a taxpayer needs to correct the original Form ST-1 filing or a previously filed Form ST-1-X.

A claim for credit or refund for an overpayment of occupation and use tax may be filed on or after January 1 and July 1. No amount of tax, penalty, or interest erroneously paid more than 3 years prior to such January 1 and July 1 shall be credited or refunded, except that if both the Illinois Department of Revenue and the taxpayer have agreed to an extension of time to issue a notice of tax liability as provided in Section 4 of the Retailers’ Occupation Tax Act, such claim may be filed at any time prior to the expiration of the agreed upon period. 35 ILCS 120/6.

For example:

• If a taxpayer filed Form ST-1-X claiming a credit or refund between January 1 and June 30, the claim period encompasses the amounts the taxpayer overpaid during the current year and previous 36 months.
• If a taxpayer filed Form ST-1-X claiming a credit or refund on or after July 1, the claim period encompasses the amounts the taxpayer overpaid during the current year and previous 30 months.

Effective June 25, 2021, for any period included in a claim for credit or refund for which the statute of limitations for issuing a notice of tax liability under the Retailers’ Occupation Tax Act will expire less than 6 months after the date a taxpayer files the claim for credit or refund, the statute of limitations for issuing a notice of tax liability is automatically extended for 6 months from the date it would have otherwise expired. 35 ILCS 120/6.

Note: The postmark date is used to determine whether a properly amended return (i.e., claim for credit) has been timely filed.

If you are making an additional payment, please note that the longer you wait to pay, the more interest and, when applicable, penalty you will owe. 

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