Regarding IRC Sec 645 election, when is Form 8855 due exactly?

[kmd]

I have read that Form 8855 is due by the first estate income tax due date.  So, since estate income tax operates on a fiscal year, if the decedent passed on 9/16/2020, then the end of the fiscal year is 8/31/2021, correct?  And taxes are due by 12/15/2021.  So, does this mean that the 1041 along with the IRC Sec 645 option and Form 8855 attached is not due until 12/15/2021?  Do I not need to do anything by this 5/17/2021 calendar date?  I don't need to file th eForm 8855  by 5/17/2021?  I am not ready to fille 1041 - have not completed distribution of trust assets.  Note this was a QRT, and all assets in trust, nothing in estate/probate.  No probate.  Trust is straightforward, but it will have income.  Can I do nothing at the IRS level until 12/15/2021 and just work on getting everything handed off to beneficiaries such that nothing remains that is owned by the TIN?  Thanks.

[M-MTax]

If there is no related estate why bother with the election? Just file the 1041 for the trust.

[kmd]

Thanks for your response.  From what I've read, there are multiple advantages.  $600 deduction instead of $100.  No estimated tax is due (estimates required for trust income, not for estate income).  It prevents having to file more than one 1041 potentially (otherwise, one is due for 2020 and another for 2021).  The trustee has not finished distribution of assets and needs more time.  This is probably the main advantage - the ability to defer paying taxes and push out the date that the 1041 is due via the fiscal year option.  But it seems like submitting Form 8855 would be something that's necessary at the calendar year date just to let the IRS know that's what's happening with the TIN and post-death income remaining from 2020 on which taxes are owed.  Yet everything I've read indicates it's not due until the fiscal year of the estate.  Perhaps it would not hurt to submit the Form 8855 alone by 5/17/2021 - it seems like a stand-alone form requiring signature yet it's often referred to being attached to 1041.  But then I'd attach it again to the 1041 when that is due (12/15/2021) since it seems it's always required when taking the IRC Sec 645 election.  Thanks for your input.