How do you check on cp21b refund?

To check the status of your CP21B refund, you can visit the IRS website and use the "Where's My Refund?" tool, which allows you to enter your Social Security number, filing status, and refund amount. Alternatively, you can contact the IRS directly by phone for assistance. Make sure to have your tax information handy for quicker service. Additionally, you may want to check your mail for any correspondence from the IRS regarding your refund.