This was an issue last year copied here "
The question is why does Turbotax take away the efile option, given that the form 3520 is sent via paper and is NOT to be sent/filed along with the return as per the IRS filing requirements?
The solution should have been to let people still eFile and the Form 3520 would need to be anyway sent separately via paper mail.
This seems to be a limitation in Turbo tax's implementation.
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THIS PROBLEM is still here for 2024. Any intention to resolve?