Did you enter unemployment compensation?
Go to this IRS website for information on the unemployment compensation exclusion - https://www.irs.gov/forms-pubs/new-exclusion-of-up-to-10200-of-unemployment-compensation
Did you receive a Form 1095-A for health care coverage from one of the state Marketplace Exchanges?
Go to this IRS website for the Premium Tax Credit adjustment - https://www.irs.gov/newsroom/irs-suspends-requirement-to-repay-excess-advance-payments-of-the-2020-premium-tax-credit-those-claiming-net-premium-tax-credit-must-file-form-8962