Per the IRS form 1040 instructions page 76
https://www.irs.gov/pub/irs-pdf/i1040gi.pdf
If your return is signed by
a representative for you, you must have
a power of attorney attached that specifically
authorizes the representative to
sign your return. To do this, you can use
Form 2848.
TurboTax does not support the 2848 form but it can be downloaded from the IRS site.
Form: https://www.irs.gov/pub/irs-pdf/f2848.pdf
Instructions: https://www.irs.gov/pub/irs-pdf/i2848.pdf
Per @macuser_22
THE TURBOTAX ANSWER WAS "WE DON'T SUPPORT FORM 2848"......YOU SHOULD
NO AND THEY WILL NOT EVER ... since most married couples simply efile a joint return and the one spouse that can complete the return would simply enter a 5 digit number for the other spouse in the program. The form 2848 is typically used solely on paper returns.
The question was about CA 540, not IRS 1040, so what is the answer?
No, unfortunately, you cannot submit the CA-3520 (California POA) electronically with TurboTax. You can complete it separately and mail it to FTB.
See 2024, FTB 3520 PIT Individual or Fiduciary Power of Attorney @PaulCongdon