The Government may, by notification in the Official Gazette, add to or omit from any Schedule any entry or entries or transpose any entry or part of entry from one Schedule to another or vary any entry or entries or the rate or rates or the point or points of levy or otherwise amend or modify any Schedule, prospectively or retrospectively, and thereupon the Schedule shall be deemed to have been amended accordingly:

Provided that the Government shall not vary the rate of tax so as to enhance it, in any case, exceeding forty paise in a rupee.