Go here and you will find instructions:
TurboTax Accuracy Guarantee - TurboTax® Software Support
The link to file the claim is here (and on page above):
FAQ on the Guarantee is here:
"You must contact us within 30 days
of your penalty assessment if you believe a TurboTax calculation error has occurred. Do not wait to respond to the tax authority.
The TurboTax Accuracy Guarantee is a reimbursement program. If after reviewing your claim, it is determined that TurboTax made a calculation error, Intuit will reimburse you for the interest and/or penalties you paid to the IRS or state tax authority. Intuit does not pay any additional tax liability you may owe."
Seems like you should respond quickly.....