@Critter-3 has the right idea, but there is an issue:
The investments (stocks, bonds, et al) might have received a stepped-up basis on the death of the mother and the brokerage statement might not reflect the new basis. Further, the holding period for property acquired from a decedent is automatically long-term and the 1099-B may not reflect that (for some securities) either. If so, then the data need to be entered manually, regardless.
