What is the ruling on incentives and commissions based on sales in a sales representative job, and are they permissible, or do they fall under the category of prohibited gambling?

If the annual increase and commissions are part of the agreed-upon lease and rental contract, then it is impermissible because the rent would be unknown, and an unknown rent invalidates the contract. It is a condition for the عوض الإجارة (consideration for the lease) to be known. However, if these percentages are not linked to the original contract and are given as a reward to employees when sales targets are met, then we hope there is no harm in it, and it would fall under the category of جعالة (a stipulated reward for performing a specific task).