Find Form 1099-INT, also called "Interest Income" form, or Form 1099-OID, also called "Original Issue Discount" form. One of these forms should have been sent to you from the bank or financial institution that holds the interest you've made.
Look to line one on Form 1099-INT to find your taxable interest for the year. Look to line one and two on Form 1099-OID to find your taxable interest for the year.
Call or visit your bank or financial institution if these forms haven't been sent to you or you're looking for the taxable interest you've made in previous years. Find your bank or financial institution's customer service phone number by navigating to their website and clicking on the "Contact" option. Your bank or financial institution will need to confirm your identity before they provide the information you're looking for. Be sure you're ready to provide account numbers and any associated passwords before you call.