Emphasis is to be laid on whichever is higher (I agree with Sh.Amit Agrawal, Sir)
An illustration
Suppose capital goods (machinery) was purchased for ₹ 12,00,000/- and Rate of tax was 18%. So credit of ₹ 2,16,000/- was taken. Supposing machinery was used for two years (8 quarters). Entitlement to retain credit @5% per quarter under Rule 40(2) is ₹ 86,400/- i.e. 40% of 2,16,000/-. Balance of credit to be reversed is ₹ 1,29,600/-
HYPOTHETICAL OPTIONS
(i) Now suppose scrap of capital goods is sold at ₹ 2,00,000/- attracting rate of tax is 18% and tax is ₹ 36,000/-. Whichever is higher is to be paid/reversed i.e. 1,29,000/-
(ii) If the said scrap is sold for ₹ 8,00,000/- (transaction value), tax @18% works out to ₹ 1,44,000/-. Then the assessee will pay total GST amounting to ₹ 1,44,000/- (whichever is higher).