if you used summary totals (code M) on form 8949 then you haven't provided the details the IRS requires. that would come from submitting the 1099-B along with the form 8453. if none of the lines are coded M (column F) on the 8949 then just ignore the prompt.
Exception 2. Instead of reporting each of your transactions on a separate row of Part I or II, you can report them on an attached statement (or file form 8453 with the details if not mailing your return) containing all the same information as Parts I and II and in a similar format (that is, description of property, dates of acquisition and disposition, proceeds, basis, adjustment and code(s), and gain (or loss)). Use as many attached statements as you need. Enter the combined totals from all your attached statements on Parts I and II with the appropriate box checked. Don't enter “Available upon request” and summary totals in lieu of reporting the details of each transaction on Part I or II or attached statements (mailed with return or 8453 if e-filed).
