Sir, why do we consider consideration payable to customer in exchange of goods or services as a purchase transaction and also why do we consider it as a reduction in transaction price?
In IFRS 15 “consideration payable to a customer” includes coupons/vouchers, refunds and discounts. For example:
X buys £100 of goods in a retail store W and receives a £7 voucher to be redeemed against his next shop. Under IFRS 15, W accounts for only £93 revenue. The £7 will be recognised only if the voucher is not redeemed.