First, you should call the provider of this Form 1099-B, just to make sure that the amount in Box 1d is actually a negative amount.
It is possible that this could be a negative amount, since Box 1d displays cash proceeds, reduced by any commissions or transfer taxes related to sales.
That said, TurboTax online won't allow you to enter a negative amount, although TurboTax desktop appears to. This issue is being looked into, as other TurboTax customers have related a similar experience.
Edited 02/17/2017 11:05 a.m.
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