I e-filed Federal 1120 with no problem. It navigated me to the 8453-C form, which I printed out, signed, scanned, and submitted a pdf of it.
But after completing the California Form 100 and clicking to e-file, it took me directly to the final stage of ready to file, this can't be reversed. But it never asked me to print scan and submit a California efile return authorization for corps - 8453-C
"Why is turbotax 1120 not asking for 8453-C when e-filing California?"
But, per that link, it confirms that the signature authorization Form 8453C is definitely supported In connection with e-filing the California Form 100. In fact, when I’ve completed the Form 100, it gives me the option to either mail or e-file, but when I select the file, it never gives me the opportunity to download and PDF the form 8453C. Instead it simply goes straight to e-filing. I am reluctant to do that because, there would be no signature authorization to accompany it.