The IRS letter should tell you the reason why is was disallowed - what did it say?
The letter said that there is an error on calculation on my from 8880 ( credit for retirement contribution) and I can not find the error. I redo my tax return two time and I have same amount of credit.
The letter should tell you exactly what they thought was wrong. If not then call the number on the letter for more information. Nobody here can see your tax return to determine if there actually was an error of not. The IRS does make mistakes.
Turbo tax calculated the form 8880 ( retirement tax credit). Now IRS said that there is an error on computation of the credit on form 8880. I just have a simple tax return.
IRS found the error and corrected it.
You'll just have to live with the change made by the IRS. unless you choose to dispute it in writing.