It's now 6 years after this question was initially posted to TurboTax and this bug is still not fixed. I'm going to do my best to summarize the Expert responses here:
@IsabellaG : This DOESN'T matter (but no guidance for what value to put there, since you still have to enter it)
@DaveF1006 : This DOES matter (Next post - try just entering 0 anyway)
@JohnB5677 : This DOESN'T matter
@VictoriaD75 : This DOES matter.
@PattiF : This DOESN'T matter (even though the IRS explicitly says that it does)
@RobertB4444 : This DOES matter, and putting 0 could have important implications even if your stocks are > 1 year old (though not for most people)
It is very disheartening to come back to this after 2 years with no resolution whatsoever. To me, this seems conclusively like a TurboTax bug - the IRS very specifically says to leave this field blank.
(https://www.irs.gov/instructions/i8283)
Column (g).
Do not complete this column for publicly traded securities held more than 12 months, unless you elect to limit your deduction cost basis. See section 170(b)(1)(C)(iii). Keep records on cost or other basis.
Yet TurboTax does not give that option! 0 is NOT the same thing as blank. My current understanding is "putting 0 is probably fine for most people, I think", but that's not an answer, just a workaround. To be clear though, I'm just some person doing his taxes - I really don't know what I'm doing and could be totally wrong about any of this. But sadly this thread doesn't really help get any answers.
I would really appreciate this bug to be fixed, and better clarification about this problem.
