Can Excess Reversal reclaim under rule 42

Based on the information provided, it appears that you have claimed a reclaim of excess Input Tax Credit (ITC) reversal in the amount of Rs. 20 (120-100) for the financial year 2018-19. However, according to the notice you received, there is no provision for reclaim of excess ITC reversal.

It could be that in your GSTR 3B filing for the financial year 2018-19, you had accidentally entered an incorrect amount of Rs. 120 for the ITC reversal instead of the actual amount of Rs. 100. And then you claimed a reclaim of Rs. 20 (120-100) which is not allowed as per the GST laws.