After you file

the input of data and answers to questions are done made by the taxpayer. Turbotax only does calculations based on what was entered. so is the error the taxpayers or did Turbotax make a calculation error?

I source to determine what happened or you could hire your own tax pro.

The Audit Defense service is provided by TaxResources, Inc., also called TaxAudit.com, in partnership with TurboTax. If you paid for Audit Defense and you received an IRS notice, call TaxResources, Inc. at 877-829-9695, or report your IRS notice on their website at http://intuit.taxaudit.com/. Do not contact the IRS until you have spoken to TaxResources. They may contact the IRS on your behalf.