@ryzen674
If you had thousands of trades, you probably will not be able to import, because TurboTax can't handle it.
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At tax time, you have the option to summarize your activity by Sales Category.
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.
Category A and D are the covered transactions.
(your paid preparer should have known that, and now you know it too.)
If you summarize (recommended),
you only need to supply details of 1099-B covered transactions with adjustments that are not listed on your e-Filed Form 8949. and all non-covered transactions not listed there.
In other words, for active investors, generally this is a list of the Wash Sales.
Note: TurboTax 2020 may suppress some covered transactions without adjustments that you entered in detail. For those, no mailing is required !
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If you have two pages (for example) of Wash Sales,
use Adobe Reader to print those two pages. That's all you have to mail to the IRS, given that those wash sales are not on your e-Filed form 8949 already.
(you might enter them manually if they are few in number.)
If you were wise enough to avoid wash sales, you won't have to list or mail anything.
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Meanwhile, it's been reported that TurboTax Online 2020 will take your 1099-B PDF as an attachment avoiding the need to mail it. But TurboTax CD/download will not.
TurboTax 2021 remains to be seen.
