What is the legal ruling regarding opening an exchange shop that cashes post-dated checks for customers in exchange for a 1% commission, in order to avoid paying the 17% Israeli taxes, knowing that the exchange shop pays commissions to the bank when withdrawing cash? And what is the Sharia-compliant method for such a transaction?

A check is a commercial paper of guaranteed value and a legitimate documentation of debt. When its value is paid by a third party, the same value must be repaid along with administrative expenses as a lump sum, not as a percentage of the check's value, to avoid usury (riba). This also applies to post-dated checks. It is permissible for check holders to cash them under the aforementioned condition when they are compelled to do so, and the sin lies with the exchange companies.