I've been attaching an 8543-S form with e-filing for several years. At the top of this year's 2019 8543-S form is the same as previous years: "File electronically with the corporation's tax returns. (Don't file paper copies.)". This doesn't seem to agree with the answer you received "The support team advised that form 8453 is not a supported form for e-filing". If you have a way to contact them again, can you ask why their answer doesn't agree with the top of the 2019 form? Thanks.
