With B2B Payments enabled, customers placing orders through your B2B Commerce platform will be given the option to either pay now or pay later as part of the checkout experience.
If they choose the 'Proceed to Checkout' option to pay now with a debit or credit card, your customers will be presented with a B2B Payments page used to capture their payment details and process the payment.
If they choose to 'I'm Done' option to pay later, the order will be created within your QuickBooks Commerce account as per normal. Once the order is finalized and invoiced, you can email your customer (i.e., the Buyer) the invoice directly from QuickBooks Commerce.
B2B Payments supports partially paid invoices, meaning that if an invoice was partially paid for manually, you could use B2B Payments to complete the process.
Next, QuickBooks Commerce will generate an email to be sent to your buyer according to your branding:

The buyer can click 'View and Pay Invoice' to access the invoice details as shown above.
You will be posed with this page to check through the details and click on ‘Pay Now’ to make payment.

The invoice details are shown on the left-hand side. Enter your payment details on the right-hand side. Fill in all the details accordingly and ensure that the name on the card is valid and accurate. Then, click on 'Pay Now'. Please stay on the page while the payment is being processed.
If the payment is unsuccessful, QuickBooks Commerce will indicate an error message, briefly explaining why the payment is unsuccessful.
Once the payment is successful, the invoice will be indicated as ‘Paid’.
If you wish to control the visibility of B2B Payments for Buyers, read this article.