Yes, you do need to mail your supporting statements, such as your brokerage statements (Form 1099B) with Form 8453, but you don't need to include Form 8949 since TurboTax filed this form electronically with your tax return. You can include it for reference purposes, if you like.
When you use the summary method, TurboTax produces a Form 8949 with the summary totals that you entered, not the individual transactions, so Form 8949 that is included in your e-filed return is NOT sufficient for this purpose. This is why you are required to mail in Forms 1099-B.
It's always a good option to send documents to the IRS by a method that provides tracking information.
Note that you must postmark this mailing no later than three days after your e-filed return is accepted by the IRS.
Any Forms 1099-B that you uploaded to TurboTax are not sent to the IRS with your e-filed return. This step saves your forms with your online tax return for your future reference.
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