According to IRS.gov, you may have already received or will be receiving an unexpected deposit into your account from the IRS. The IRS has been issuing interest payments averaging $18 to roughly 13.9 million individuals who filed a 2019 return by July 15 of this year and either received a refund in the past three months or will receive a refund in the coming months.
This payment will be made in the same manner as your tax return (direct deposit or physical check), and there will be a notation on the check saying “INT Amount”. This notation will identify the deposit as a refund interest payment and will indicate interest amount.
You can read the full article from the IRS here.