the cost and purchase dates aren't showing on my 1099-B but I know them. It is flagging me to fill in those boxes. Am I allowed to alter the 1099-B by filling those in?

[juliecarlton11]

Turbotax is flagging me to review and fill those in, even though I answered later that I know the cost basis and filled it in on the following page.

[ThomasM125]

You can enter the correct cost basis and dates acquired even if they are not listed on the Form 1099-B. If you continue to have trouble with the entries you may need to delete them and re-enter them.