The tax return itself can still be electronically filed when Form 8453 with transaction detail is mailed.
In either version, if a large volume of transactions were involved and entering a summary of the transactions into the tax return was preferred, the detail would be mailed to the IRS with Form 8453.
Form 8453 is like a cover page telling the IRS what is being submitted. Your statements with all the transaction details are sorted on Forms 8949 based on the type of transaction, covered or non-covered, and the length of time the asset was held, short-term or long-term. TurboTax automatically sorts the summaries or transactions to Forms 8949 as necessary.
For more information, see: Do I need to fill out or mail in Form 8949?
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