When I report capital losses in my tax forms do I've to to list every company I traded with? I did not keep track of my losses or gains for each stock but only my total gain/loss and I've traded over 1000 different stocks so it's gonna be quite annoying if I gotta list each and every one of them.
You should provide a list of all transactions. Contact these guys for help. http://www.gainskeeper.com/
You may be able to attach your brokerage 1099 electronically to your return and just report the summary numbers from it. Ask your CPA. Alternatively, you can see about downloading the transaction details for Form 8949 from your broker, which should have the taxable trade level details. Honestly, I don't think the IRS wants 100-200 pages of 8949 transactions, although you should have that information if requested. Also, I hope there are more profits than losses if you're trading that much. Otherwise, I might recommend you revisit the First Rule of the Hole.
If you were given a K-1 by the company/ ies then all you have to do is report the loss and not the transactions, barring that you'll have to fill out Schedule D.