It sounds like you initially reported your investment sales transactions by category totals. When you do that you have to either mail Form 8453 with a copy of your 1099-B and Form 8949 or, if you are using TurboTax Online you can upload a copy. But once you transmit your return via e-file, you cannot make changes or add attachments (unless it is rejected for some reason. You will have to mail Form 8453 and your 1099-B
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