custom Duty payment

recently I'm doing Audit of a company where I found a query related to custom duty payment.
The company paid a custom duty of Rs.50 lacs and this duty is related to import of FY 2018-19.
They expense out the total payment of custom duty in the FY 2017-18.
as per my opinion the treatment is wrong bcoz the payment of duty must me treated as advance payment.
The treatment is correct or not given by management??