Assume it is given that you need to itemize trades on, say, Form 8949 (+ any state form(s)). These forms only allow so many transactions per page (14 entries for Form 8949).
How exactly do people who have thousands of transactions to itemize (or tens or hundreds of thousands...) deal with this? Does the IRS really want to receive hundreds or thousands of pages of transactions?
And I suppose people e-file if they are willing and able to, but what about those who prefer to and/or are required to file by mail? Do they send entire reams of paper to the IRS? Or do federal & state governments provide a more practical solution?