How can I submit my hardship exemption certificate number (ECN) if I already submitted my taxes?

[michelle-truong9]

How can I submit my hardship exemption certificate number after I had already submitted my 2018 taxes? 

[HelenaC]

If you didn't get a letter from the IRS requesting the exemption certificate number, you'll have to amend your income tax return. See How to amend (change or correct) a return you already filed