Prior period expense

In Income Tax you may not get deduction as perior period expense or you can not claim as a deduction in current year .

Expenditure is relating to ..Goods or service..?

Want to know treatment of both goods and service 

Prior period expenses are not allowed in current year untill and unless the expenses have crystalised during the year.

The prior period expense partaining to earlier years has been a matter of litigation whether such expense could be allowed as deduction during the current year .

if specific to your case, Bill is of 31st March, 2020 but received in May, 2020
if it's service, than if service is rendered in F.Y 2019-20 and invoice is also issued in that year, than that is prior period expenses and disallowed.
But if it's relating to Goods, invoice of last year, but goods received in current year than it's considered as current year expenses.

Sir please tell me the meaning of expense crystalized during the current year?