Legal Question in Banking Law in California

It depends how large the estate is. If it's a "small" estate, then letters testamentary are not necessary. You would just do an affidavit if it's more than 45 days after the person's death. If the amount exceeds the limit, then you'd have to file for probate of the estate, and ask the court to issue letters testamentary -- i.e. to be the administrator of the estate.