Well, you can make your checkout payment options only accessible to the selected customers with PayRules: Hide Payment Methods app by utilizing customer tags. For instance, you can give your selected 40 customers a specific tag and then only the customers with that tag can see and use your payment method at the checkout page. Here are the steps you need to follow:
- Choose your checkout method (Invoice for example) from the Select payment methods or Additional payment methods field.
- Choose Hide if not found under the Customer tags field.
- Now enter the customer tag (Selected for example) under the Customer tags field.
Hope it serves. Thank you.