What is the ruling on cash back given at a random percentage after the completion of a transaction, the value of which is not known until afterwards? Is this considered gharar (excessive uncertainty/ambiguity)?

It is impermissible to engage in "cashback" transactions unless the refund percentage is a gift from the electronic payment provider, serving as marketing incentives, encouraging rewards, and promotional gifts. In this case, it is permissible according to the preponderant opinion of contemporary scholars. However, if the refund percentage is part of the fee and not a gift, then these transactions are impermissible due to the presence of gharar (excessive uncertainty).