For the 2020 return, if the taxpayer had unemployment that later became fully or partially non taxable which means they are now eligible for a credit they were not eligible for on the original return and/or they fail to enter the correct 2019 AGI to get the credit thus the IRS sends the form 15111 to alert the taxpayer they "may" be eligible for a credit they did not already apply for. This is in the taxpayer's favor as it saves them from amending a return they may not know it needs to be amended.
