You need to file amended tax return if you need to make changes in your originally accepted tax return. For example, Joe e-filed his federal tax return, and his tax return was accepted by the IRS in early February. Later on in March, Joe discovered he forgot to report $500 interest he received from the bank. Because his tax return was already accepted by the IRS, Joe would need to file amended return for that change.
Do not file Amended Return because you received rejection when e-filing your tax return. When receiving efile rejection, you need to make corrections then resubmit your tax return for e-file again.