@malcolmanthony
See the info I just left you above.
If you need additional help with this matter, you may wish to phone TurboTax free Audit Support Center. While your issue is NOT an audit, that center also helps people deal with IRS letter issues, and they should be able to question you in realtime and advise you on responding to the IRS letter.
To get the phone number, go to the page linked below and click the blue "Get Help" button. Then follow the prompts to get the number. Hours are 5AM-5PM Pacific (8AM-8PM Eastern) Monday-Friday.
https://support.turbotax.intuit.com/irs-notice/audit-support/
