Substantial question of law: appellate review allowed where such a question exists, hearing limited to the formulated issue. An appeal to the High Court lies from an Appellate Tribunal order when a substantial question of law is involved; it must generally be filed within one hundred and twenty days by a memorandum precisely stating that question, though the High Court may admit late filings for sufficient cause. The High Court formulates the substantial question, hears the appeal principally on that question (while allowing respondents to contend it is not involved), may decide other substantial legal questions for recorded reasons, determine issues not or wrongly decided by the Tribunal, award costs, and its judgment is to be given effect by the Assessing Officer; Civil Procedure appeal provisions apply as far as practicable.