If the holding period was 12 months plus one day, the program should be able to recognize the holding period and not require the amount. However, since it is not, I am guessing the software is requiring the value due to prior customers with short term holding missing the field. The programmers must sometimes mark boxes as required to ensure the success of the masses.
Double check your date acquired and date of contribution are at least 12 months plus one day.
You can try entering 0 as the basis (or the actual amount) to satisfy the software filing rule. Providing the data does not invalidate your tax return. The IRS will gladly accept your return without repercussion for this value.
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