@stwpcw60 wrote:
This is a complex electing trust. How do we tick both the "decedent's estate" box and "complex trust" box?
You do not and what you are describing is not the proper procedure for a Section 645 election.
You need to check Box G in Forms Mode and provide the TIN for the trust. You also need to file Form 8855.
Frankly, and to be quite blunt, you are way out DIY territory and absolutely need to consult with an experienced local tax professional and legal counsel.
See also https://www.irs.gov/instructions/i1041#idm140229121819120
