The query may be explained through below example -
Cost of capital goods say ₹ 1000/-, amount of GST say @ 18% i.e. Rs. 180/- and the capital goods is used for exclusively exempt supplies, hence not availed any ITC. Let say, after a period of one year (i.e used for 4 quarters), the same capital goods is supplied.
On the above scenario, GST liability shall be higher of below -
(a) GST @ 18% on transaction value; or
(b) Amount of GST as reduced by 20% [i.e. ₹ 180 - (180 * 20%)] amounting to ₹ 144/-
Here, the selling dealer (supplier of old capital goods) shall be entitled to take ITC of ₹ 144/- as the goods is supplied even if used for own use for a period of one year.
In the above example, if the goods shall be supplied at ₹ 900/-, then amount of GST liability @ 18% on transaction value shall be ₹ 162/- (i.e. being the higher of ₹ 144/-). And the net GST liability shall be Rs. 18/- after utilizing ITC of ₹ 144/-.