Adjustment of excess itc to be reversed with excess output tax paid

Respected members,
My client in 17-18 took a stand that he had paid excess output tax and had availed excess ITC.
The excess ITC had to be reversed so he adjusted the excess itc to be reversed with excess output paid and reversed the net excess ITC.
This effect was given by his previous auditor in form 9C.
Is this sustainable or we should suggest him to use excess output paid for discharging liability of 18-19 and reversing the actual amount he was supposed to reverse as excess ITC availed.

Please guide