there is nothing wrong with using lines 1a and 8a (I wish that worked when importing from my broker rather than needless pages of form 8949) . that's a summary of transactions when 1) proceeds are reported to the IRS 2) cost basis is reported to the IRS 3) and there are no adjustments either by broker or taxapayer like for wash sales. For these trades, NO detail needs to be sent to the IRS not even the 1099-B as either an attachment to a mailed return or with form 8453 if e-filed.
all transactions of any type with any adjustment must be reported separately or detail otherwise provided to the IRS. Code W indicates wash sales. If separately reported on form 8949 no detail needs to be sent to the iRS. If grouped (code M - multiple transactions reported on same line) and any other lines coded with M details need to be sent to the iRS.
