My 8949 is 600 pages which is less than 50 transactions because I'm a Bitcoin miner and it uses thousands of tiny Bitcoin deposits to calculate my cost basis for just a small number of sales. The Aggregated 8949 should be a menu option. Also, in the event someone has a lengthy 8949, I think your system should alert them to the fact they can get an Aggregated 8949. If they request 8949 and it's lengthy: System prompts user: Your 8949 is 600 pages, we recommend the Aggregated 8949 instead. I think you should prompt the user whether to even generate the report before wasting system resources. The 600 page report is too long and large to e-file since the IRS has a file size limit (I think it's 1.5MB). The Aggregated report will allow you to e-file your 8949. Otherwise if you e-file your 1040, you will have to file Form 8453 within 2 days of your tax returns being accepted by the IRS and mail it with your printed out 8949.
