Thank you for your question.
There used to be a law that allowed you to choose the date in which to treat the gain or loss of securities sells, if the date of sell was different than the settlementn date or date of receiving the revenues. However:
The Tax Reform Act of 1986 (TRA) added Sec. 453(k), which requires that income and loss on publicly traded securities be recognized in the year of disposition (trade date).
form the IRS website we find that:
purposes by both cash and accrual method taxpayers on the date the trade is executed.
What this means is that the former alternative methods have all become obsolete. You can no longer treate gains in the following ways: