The Illinois Certificate of Error application For Taxable Properties is a form designed to allow property owners to apply for a reduction in their assessed property taxes. This form can be submitted to the local county assessor's office to request a reduction of property taxes due to an error in the assessment. The application must be filled out completely and include any supporting documentation or evidence that can be used to demonstrate the assessment error. There are two types of Illinois Certificate of Error application For Taxable Properties: the Request for Abatement and the Request for Refund. The Request for Abatement is used when the property owner believes the tax was incorrectly assessed and the Request for Refund is used when the property owner believes the taxes were paid in error. Both requests must include detailed information regarding the error. In addition, the property owner must provide proof that the error actually occurred and provide any additional evidence that can be used to support the claim.