This practice note provides valuable practical tips to keep in mind when completing an Application for a Certificate of Appointment of Estate Trustee With or Without a Will. All too often, applications are returned by the Estates Office to the applicant due to all too common errors in the file. This practice note highlights common errors made by applicants in the Affidavit of Execution of Will or Codicil, explains the Notice of an Application for a Certificate of Appointment of Estate Trustee with a Will (including who it must be served on) and the Affidavit of Service of Notice (including why it is required). It provides guidance on submitting the Estate Administration Tax and the Estate Information Return when the value of the estate is not yet definitively determined. Finally, it provides information on when security is required in the application and when security can be dispensed with.