I understand you received a deposit in your bank account from the IRS last week. There are a numerous reasons you could have received a deposit from the IRS.
First, if you had employment compensation reported on your 2020 tax return that was not excluded , that could be one reason for the refund.
Second, it could be the advance child tax credit payments that were issued last week, if you have dependents that qualify for the Child Tax Credit.
Third, the IRS also could have made a change to your filed tax return. The $1,100 could possibly be a Recovery Rebate Credit for stimulus payments not received by you.
The IRS typically mails a notice following issuing a refund with an explanation of the deposit. If you are still unsure of the deposit, you can also request a Record of Account Transcript that will reflect any changes the IRS made to a return that you filed.