Do I have to enter Non-covered Securities Code X marked as "provided as a courtesy [...] not provided to the IRS" from my 1099B?

[shinyknight]

They are listed under "Box 5- Non-Covered Securities - Code X (Unknown Holding Period)"

[DavidD66]

Yes!  You have to report all of your investment sales transactions, not just the ones that are reported to the IRS.

[fanfare]

Your transaction is reported to the IRS.

It is the "cost or other basis" amount that is not reported to the IRS.

Without basis, it is considered 100% gain. Not very courteous.

@shinyknight