Hello.
The IRS issued you a letter in order to help protect your identity, not because you used TurboTax. I was affected by that same letter last year after E-filing my return, it didn't matter what software I used, or that I actually worked for a tax software company.
The IRS simply wanted to confirm it was me that filed my return, so I visited my local IRS office and got the verification instantly. They also advised me that it would process within nine weeks, but it was faster than that in the end.
I just wanted to provide some background on what the letter is, why they are doing it and my personal experience with it. I hope this helps all of you feel more comfortable about the experience and what the IRS is doing.
For more information on why the IRS delayed your return, please visit their link regarding the letter 4883c:
https://www.irs.gov/individuals/understanding-your-4883c-letter
