Can customers complete payment prior to the due date?

Yes, you can let your customers complete payment prior to the due date by doing the following:

1. Go to WooCommerce > Payment Plans and edit the appropriate payment plan.
2. In the Payment Plan actions metabox, select the Create pending renewal order command and click the small arrow button (right after the dropdown list.)
3. Scroll to the bottom of the page, and in the Related Orders metabox, switch to the new pending order.
4. Manually edit prices for all line items (for example, if you sell one product and the remaining amount is $30, put this into the appropriate line item cell.)
5. Click the Recalculate button to update the tax values.
6. Stay on the Edit Order page, and in the Order actions metabox, select the Email invoice / order details to customer command and click the small arrow button.
7. Finally, when the customer completes the order and you receive the remaining amount, go to WooCommerce > Payment Plans and change the payment plan Status to Expired.