TurboTax Online has less capacity for 1099-B than does CD/Download.
In any case, you cannot do a 2020 tax return with Online, it is now dedicated to 2021.
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As an active investor, be aware that your category Box A or Box D sales without adjustments do not require Form 8949, so there is no reason to import or key in those transactions.
Instead use the "enter a summary" option to put your numbers on Schedule D Line 1a or Line 8a.
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If you have wash sales, it gets more complicated since those adjusted transactions have to be itemized on Form 8949 (or equivalent) and the summary totals adjusted accordingly.
