Is there anyway to use manual payments?
You need to create a 'Manual' payment gateway in Commerce &gt; Setting &gt; Payment Methods This will allow the customer to choose the manual payment method on checkout.

The 'Manual' payment method is the only way a customer can submit an order without payment information. This gateway does not place any validation on the payment form action, so you should not see any errors. If you are seeing errors, make sure you are sending the ID of the manual payment method with the paymentMethodId param to the payment form action.

The 'Mark as Complete' is a separate action that allows those that have the 'Manage Orders' permission, to turn a Cart that is in progress into an Order: