Q. In TT, should I enter the I-bond interest part of amount (already in Box 1) also in Box 3?
A. No. You should break out the I bond interest and enter it only in box 3.
It sounds like you got a 1099-int from a bank or broker, rather than from the US Treasury direct. They should know better than to include US Treasury interest in box 1. You may want to consider contacting them for a corrected 1099-INT.
