You can use "Cash on Delivery" as an accepted offline payment method. Cash on delivery is enabled by default and available for all plug&paid accounts. You can add cash on delivery on an existing shopping cart or when creating a new one.
Note: Cash on delivery is only available for physical products only.
When you receive payment from the customer, visit your Invoices page and mark the sale as paid.
plug&paid will generate a new invoice with an updated invoice status set to "Paid".