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@lisacslater wrote:

Anyone completing the Individual return must know about the excess basis to report it as LTGC on the 1040.

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Yes, it is the responsibility of the individual person (and/or their tax professional) to keep track of their Basis.  That has always been the case.

Starting this year (the 2021 tax return), Form 7203 will be required to report the Basis calculations for a shareholder of a S-corporation.