My federal tax liability was off by $700.00 dollars. What do I do?

Did you receive a notice or letter from the IRS and for what tax year?  If so, what is the notice or letter number as shown in the upper right of the first page, usually preceded by either a CP or LTR?

we can't see your return or the notice.  it should explain the change and you could post it here but we might not be able to explain why it occurred.

it you didn't sign up for audit defense, you could still use their services for a fee

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 web site at http://intuit.taxaudit.com/. Do not contact the IRS until you have spoken to TaxResources. They may contact the IRS on your behalf.