Does the Realization of a Gain/loss on a Future Depend on the Withdrawal of Funds from the Exchange?
No, the realization of a gain or loss for tax purposes does not depend on the withdrawal of funds from the exchange. A gain or loss is realized when the contract is closed (settled, expired, or sold) or, for Section 1256 contracts, when it is marked-to-market at year-end.
The funds are considered constructively received for tax purposes.