Quote from cheeks:
Let me rephrase my question. If you did elect MTM on your stock account and investment on your futures, do you think you could defend it during an audit? My concern is that they would see two actively traded accounts and the red flag would go up.
From what I understand, if you trade both securities and commodities, then you have two occupations. One is "securities trading" and one is "commodities trading." When you elect MTM, you must specify that you are electing it for your "securities trading" business (and not for "commodities trading"). If you do this, your commodities trading will naturally be marked-to-market and you will receive 60/40 tax treatment. However, if you don't do so well in a year trading commodities, I believe your capital losses (for commodities) will be capped to $3,000 (since you didn't elect MTM for your commodities trading). The MTM election is made separately for securities and commodities trading.
I am assuming that E-mini S&P and E-mini Nasdaq 100 futures contracts are considered commodities and not securities since they are treated as 1256 contracts. Please correct me if I am wrong.