after you comp TurboTax and the brokerage statement on non-professional trades, the difference is not meaningful, fifo lifo and average. i don’t bother.
10,000 transactions? That's nothing In the technical documentation for WinZIP, you'll find this gem: We recommend that if you are going to be using the same password to encrypt very large numbers of files with WinZip's AES encryption (that is, files totaling in the millions, for example 2000 Zip files, each containing 1000 encrypted files) you use 256-bit AES keys rather than 128-bit AES-keys. The technical reasons for this are discussed below. One purpose for the "salt" values used with WinZip's AES encryption is to yield different encryption keys for each file, even if multiple files are encrypted with the same password. With the 8-byte salt values used with WinZip's 128-bit encryption it is likely that, if approximately 4 billion files are encrypted with the same password, two of the files will be encrypted with the same key. Someone who obtained copies of two files encrypted with the same key could learn information about their contents, so it is advisable to stay well below this limit. Can't make this shit up https://kb.winzip.com/help/help_encryption.htm
That's what I've always done, even before it was allowed. I just attached a note saying if they want me to submit a stack of papers thicker than a phonebook... call me and I'll send a thumb-drive and "you can have at it with your printers." Never heard a word back in 20 years.
Just FYI: I think for > 20 years, I have NOT filed trade x trade with IRS. Like you, there were times when that would be > 200 pages. For all those years, accountant would just write "available upon request." For whatever reasons, returns were never quested due to missing trade x trade.
The broker already sent the 1099 to IRS, unless your own numbers have a large discrepancy, they don’t bother.