801.This paragraph provides for cases to be re-heard by an appeal tribunal where the tribunal has made an error of law or where the parties to an appeal agree that the tribunal has made an error of law.
Sub-paragraph (1) provides for cases in which an appeal tribunal can redetermine an appeal as being those where an application for leave to appeal from a decision of an appeal tribunal has been made to the person who constituted, or was the chairman of, the tribunal when the decision under appeal was given (or, in prescribed cases, such other person (apart from the Commissioner) as may be prescribed).  Sub paragraph (3) allows that person to set aside the decision under appeal, if he considers that there was an error of law, and to refer the case for redetermination by the same, or a differently constituted, tribunal.
Sub-paragraph (3) requires that a decision be set aside and redetermined by a differently constituted tribunal where each of the principal parties to the appeal express the view that there was an error of law.
Sub-paragraph (4) defines who the principal parties to appeals are for the purpose of subsection (3) above and for paragraph 8, namely:
It is intended that regulations under sub-paragraph 4(a) may provide, for example, that where a case is drawn to Secretary of State’s attention in which he believes there has been an error of law, he may draw that fact to the appeal tribunal’s attention, even though he is not an applicant for leave to appeal.
Regulations made under paragraph 23 would define who is a person “affected” for the purposes of this Schedule.
Part III: Social Security Administration Housing Benefit and Council Tax Benefit Schedule 7 Paragraph 7: Redetermination etc. of appeals by a tribunal