1. Sale on 30th march is with condition that if party pay before 5th of April will get 10% discount.
2. As the amount and % of discount is known, on the date of Sale the amount of dicount can be reasonable calculated.
3. And while preparing financials, events between the end of the financial year and date of approval by the board should also be considered.
So, a provision should be made for the discount amount at the end of the financial year.
Otherwise your profit is overstated.