It is possible to create an On Account sale in Vend.
Create the sale
Do this by ringing up items as you normally would, and before hitting the 'Pay' button, ensure you have entered the customer name.
When you hit 'Pay' choose the 'On Account' option at the bottom of the payment page.
This sale will now be logged against this customer's name. Because this customer now owes money, a credit balance will be displayed underneath their name in the sell screen.
Pay the account off
When the customer wants to pay the balance outstanding on this sale, open the sale by locating it in the 'History' screen or under the Customer record, and hit 'Open'. This will open it in the current sale screen.
Hit 'Pay' and choose the relevant payment type, e.g. Cash.
The customer's balance outstanding will now be reset to zero.
Vend will automatically post these On Account sales and payments to Xero.