Filed in 2016 but just got a $1000+ bill for Colorado Capital Gain Subtraction prob. CO Rev Dept said my house purchase date doesn't qualify for Capital Gain Subtraction.

TurboTax does not receive any information from the IRS or your state after your return was filed, so no one at TurboTax knows about a letter you received from the IRS or the state.

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

TurboTax has a special phone number for help with IRS/state tax letters, which will be easier than going through regular Customer Support.   At the page below, click on the blue button that says "Get Help from TurboTax Support".  Then it will ask you what tax year is your letter.  Then it will ask you what the letter concerns. Then it will show you the phone number during posted business hours.

https://support.turbotax.intuit.com/irs-notice/audit-support/

I just got the same letter for 2017 Colorado taxes.  It appears that TurboTax did not have the correct dates programmed into their calculations.   

I also just received the same letter for the 2016 tax year.

Yes the information at https://www.colorado.gov/pacific/sites/default/files/Income15.pdf

states purchased after May 1994 and before June 2009.

However, the 2016 tax filing instructions shown here: https://cotaxaide.org/docs/2016%20CO%20DR%200104AD%20Instructions.pdf

make no mention of the June 2009 requirement.

Line 5 Colorado Source Capital Gain
Subtraction
You might be eligible to subtract the income you earned
from a Colorado-source capital gain. We recommend that
you read publication FYI Income 15 if this applies to you.
The amount of this subtraction is limited to $100,000 and
qualifies if the capital gain was:
• Earned from the sale of real or tangible personal
property that was located in Colorado at the time
of the sale transaction; and
• Included on your federal income tax return and is
calculated as part of your federal taxable income;
and
• Acquired on or after May 9, 1994 and was owned
continuously for five years prior to the sale
transaction date.

I plan to use the state's instructions for filing an appeal.

I know this is an old post but my wife and I just received a letter for the same thing.  If this is a case where TurboTax had the wrong dates programmed for the deduction is there anything that can be done to offset the interest and penalties involved?