What is the ruling on cashing checks from stores that deduct a specified percentage as commission, knowing that they cannot be cashed from banks due to not dealing with them, as they are usurious?

Cashing checks through exchange shops for a fee or commission has several scenarios:

1. The Permissible Scenario: The check is an immediate payment, and the shop cashes it from the bank for a fee or commission. This is permissible because it falls under the category of ju'alah (a promised reward for a specific task). The commission is for the service of cashing the check from the bank, and the shop is not entitled to it until the cashing is completed.

2. The Prohibited Scenario: The shop pays the holder the value of the check, deducting its commission from it, and then collects the check from the bank. This is prohibited because it involves exchanging money for money with a surplus (riba al-fadl), or it is a loan of the check's value to the customer in exchange for interest (riba).

3. The Prohibited Scenario: The check is post-dated, and the shop pays its value to the customer, then cashes the check from the bank at its due time. This is prohibited for the two reasons mentioned previously.

Summary: The permissible scenario is to agree with the shop to cash the check and collect the money from the bank for a specific amount or percentage that it becomes entitled to after completing the work and cashing the money.