Problem: Want to disable a certain payment method if the total is less than some amount.

Enter the following rule under:
**'Settings' -> 'Advanced Settings' -> 'Payment methods' -> 'Rules for the order pages'**Here you should see **'Rule for the first order page($RULE_ORDERPAGE_1)':**

Thus the payment method

if ($total_sum &lt; 100) {

DisablePaymentMethod("Invoice");

}

less than £100.00.