Your Merchant ID (MID) is provided by your payment processor or acquiring bank when you set up your merchant account. You can typically find it in the portal or dashboard of your payment processor, under your account settings or details. It may also be included in the documentation or contract you received when you registered your merchant account. In some cases, your MID could be printed on transaction receipts. If you're unable to locate it, you can contact your payment processor or financial institution’s customer support for assistance.