Sorry, I am coming to this later (Dec 2020).
I changed from "investor" to "tax trader" last year (2019).
In March of 2019 I sent letter to IRS changing accounting method/reporting.
I also filed Form 3115 with 2019 return.
Given my reading of IRS pub instructions for Form 4797 as found at URL: https://www.irs.gov/instructions/i4797
which states in pertinent part: "Report on line 10 all gains and losses from sales and dispositions of securities or commodities held in connection with your trading business, including gains and losses from marking to market securities and commodities held at the end of the tax year (see Traders Who Made a Mark-To-Market Election, earlier). Attach to your tax return a statement, using the same format as line 10, showing the details of each transaction. Separately show and identify securities or commodities held and marked to market at the end of the year."
It is my intention to file regular return electronically, with summary line on form 4797 part II, and follow it up with an amended 'paper' return to add the 20 additional pages of detailed transactions as set forth in the aforementioned set of instructions.
