One more word of advice. If your trading is not profitable, lower the amount of shares you trade to a bare minimum until you get it right and the money starts coming in. JMO
Capital losses can be carried forward indefinitely for any taxpayer. They can also be carried back, but you would have to file an amended return to do that. The principal benefit of filing under Sched C is it is easier to deduct trading related expenses. If you go Sched D, you are subject to a 2% of AGI hurdle before you can deduct trading expenses. If you or your spouse has a substantial income, that can be a real problem. Also, there is no $3,000 limit for Sched C filers on using trading losses to offset other income. Check with your tax advisor to confirm this and all other tax opinions you read.