If the Indiana Department of Revenue (“IDR”) reasonably believes that a taxpayer has not reported the proper amount of tax due, then, based on the best information available, it shall make a proposed assessment of the amount of the unpaid tax.  The  IDR shall send the taxpayer a Notice of Proposed Assessment (“AR-80”) via the United States mail. 

A taxpayer may challenge the proposed assessment, by filing a written protest (“Protest”), with the IDR, within sixty (60) days of the date of the AR-80.  The right to file a Protest is waived if the taxpayer does not respond at the AR-80 stage.

If the taxpayer does not respond at the AR-80 stage, then Indiana law requires the IDR to commence the collection process.

Indiana Code §6-8.1-5-1
Indiana Department of Revenue Tax Practitioner Resource Packet