For that kind of taxes due there must be quite a bit of income that was not reported on the original return ... review the CP2000 carefully ... if you do not agree with the IRS then follow the instructions to refute the changes.
I GOT A LETTER FROM THE IRS
https://ttlc.intuit.com/questions/3605673-i-got-a-letter-or-notice-from-the-irs
I AM BEING AUDITED
If you purchased Audit Defense:
https://ttlc.intuit.com/questions/2924451-i-bought-max-or-audit-defense-and-now-i-m-being-audited
AUDIT SUPPORT
https://support.turbotax.intuit.com/irs-notice/audit-support/
