if you received a CP2000 it's likely the IRS increased your adjusted gross income (the real change). As a result of that change your deductible medical expenses would go down.
TT guarantee wouldn't apply if you didn't report all your income.
if you do not understand the notice
What to do
You generally have 30 days to respond to an IRS notice, so there's no reason to ignore it. Always check which tax year the notice relates to. Do not assume that it relates to your most recent tax return.
Follow the instructions. It may request more information or ask a specific question. If it's a minor issue and you are confident of the facts, you can respond to the notice yourself. But sometimes, you may need to seek help from a tax professional. The IRS says in its article "Eight Things to Know if You Receive an IRS Notice" that "most correspondence can be handled without calling or visiting an IRS office."
If you filed the tax return with TurboTax, you can take advantage of our free audit support options. Our "Audit Support Center" walks you step-by-step through responding to an IRS notice.
https://support.turbotax.intuit.com/irs-notice/audit-support/?TB_iframe=true
If you agree with the correction notice
If you make a mistake on your tax return, you may receive a correction notice or an unreported income notice. Compare the IRS adjustments with the information on your tax return. If you agree with the adjustments, you can generally reply to the IRS with a check or money order for the additional taxes due. Write the reference number on the check and send it with the voucher the IRS provides with your notice.
