Turbo tax premier said it could not take a txf file that had 300,000,000 dollars in stock sales. I also traded several thousand trades in 2018. what to do?

[SteamTrain]

Would have to be Desktop since Online can only take ~500 transactions/brokerage.....Desktop can supposedly take 2000/brokerage  (but I'm not sure what it does for txf files)
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Opinion......because I'm not sure of all the details...but:

You'll probably have to go elsewhere and not use TurboTax consumer software.  (professionals with professional software can supposedly handle it)

Max $$ entry for a single field is 9,999,999.99  (but I don't know what the limit might be on multiple lines that will total over that)
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Supposedly there is a way to enter your total final result on the schedule D, and then send the IRS a stock transactions details spreadsheet on paper thru the mail. But again, your total gain for the year would have to be less than 9,999,999.99

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There are several folks more experienced in what the limits than i am...maybe they will see this and respond....and I may be somewhat off-base on some things...so be a bit leery of what I've noted above.

BUT...I don't believe we've seen anyone with $100million of anything be able to use TurboTax consumer software.

[fanfare]

TurboTax allows an entry of $300,000,000 in Form 4797 Line 1. I don't know why it is disallowed everywhere else.

[Critter]

Sorry but no DIY program will handle that kind of volume ... you will need to either complete a paper return manually  or  use a paid tax pro.

[fanfare]

No other?, Not true, other Tax software packages handle these amounts. We're not allowed to name them in this forum  . Shop around.