In Form 1040, schedule 5, line 74, I claimed $3667 credit for my repaid salary. How does IRS figure out why I claim the credit? Do I have to attach the proof?

[sadoshju]

I calculated the amount which I overpaid for 2017 Tax federal tax return and claimed as a credit. Will I be requested from IRS that I should provide details ?

[CherylW]

which credit?

[sadoshju]

I overpaid federal tax last year: Since my employer mistakenly paid me a wrong amount in 2017, I had to return the portion of overpayment in 2018. I believe that I can pay less federal tax this year. In order to do so, I calculated the difference in federal Tax between what I paid and the correct amount (calculated using the actual salary) and plan to request that amount as a federal tax credit to reduce that amount from the 2018 federal tax.

[CherylW]

Take it off your 2018 Schedule 5.  You'll have to amend 2017.

How to Amend 2017

[sadoshju]

My employer did not want to give me a revised W-2. They gave me a letter instead describing that the total amount of the salary was wrong and I returned the difference. Can I modify the amount of Box1 of W2 when I amend the 2017 return?