What does the IRS notice you received say about what the IRS has changed, added or deleted from the tax return that was filed and what tax year is the notice referencing?
What is the IRS notice number which is shown on the first page in the upper right corner and usually preceded by either a CP or LTR?
Letter says "we are auditing your 2015 federal income tax", letter #566-S, questionaires #'s13825 and 886-A
Looks like they are questioning your employee business expenses that you reported along with anything else which would have been checked on the 556-S and the 886-A.
As shown in the answer below - Contact the TurboTax Audit Support Center during business hours to get assistance in understanding the notices you received - <a rel="nofollow" target="_blank" href="https://support.turbotax.intuit.com/irs-notice/audit-support/">https://support.turbotax.intuit.com/irs-notice/audit-support/</a>
Support is open on Monday at 5am Pacific time
You may also want to obtain the services of a local paid tax professional to assist you with this audit.