I had 4 brokerage accounts. I closed 2 during 2020. I was able to import 1099B's into TurboTax for the 2 active accounts. For the closed accounts, I was unable to import into TT. So, I checked the box and used the "summary transaction" method of reporting about 15 transactions.
Everything was going well until I e-filed, at which point form 8453 was generated requesting form 8949 with supporting documentation (1099B's) for the 2 ACTIVE accounts, which were successfully imported into TT, but not for the 2 closed accounts I used the "summary transaction" input method. This seems counter-intuitive.
Unfortunately, my 2 active accounts had many trades, and I now have 6 pages of 8949's with 40 pages of 1099B's to send to the IRS. Is this the way the program is supposed to work? I should think the IRS would want to see details on the summary transactions...not the imported transactions!
