Excess payment made in 3B adjustment with short payment of GST in next financial year - Goods and Services Tax - GST

Sir One my client has received an SCN on short payment of GST in GSTR-3B in comparison to the liability declared in R1 for 2018-19. However he replied to the department that he has paid excess liability in GSTR-3B in comparison to the liability declared in GSTR-1 for 2017- 18 and a partial amount of short paid liability declared in GSTR-3B in 2018-19 has been adjusted from excess payment made in 2017-18 in GSTR-3B while rest of the short paid liability of 2018-19 was adjusted with the excess liability paid in 2019-20, however the taxpayer agree to pay interest for delay payment of GST for 2018-19 in 2019-20. Please suggest whether the client s adjustment is correct or the department s action is correct? Can the client adjusted excess liability paid shown in GSTR-3B for previous year to the short paid liability shown in 3B for next financial year?