A hedge combining index futures with individual equities creates a mixed straddle: one leg is marked to market under section-1256 while the other is not, so without relief the timing and character of the two legs diverge.
Three routes exist: electing out of Section 1256 treatment for identified positions, electing straddle-by-straddle identification, or using a mixed straddle account with a formula netting daily gains and losses. Each has its own filing mechanics and deadlines, and some must be made by the day the straddle is established.
The elections are unforgiving about timing, which is why traders running hedged books involving futures typically set them up with an adviser before the first trade rather than at filing time.
General information for the United States, not tax advice. Rules change and depend on your circumstances; take professional advice.
Related: straddle-rules, section-1256, sixty-forty-tax-treatment, form-6781, constructive-sale