When applying a partial payment to a Layby sale, these appear slightly differently from regular sales when posted through to Xero on the register closure report.
In the Retail POS register closure summary, the full value of the sale is reported, however, if only a partial payment is applied, then it is only this payment value that will post through to Xero. A summary of all layby and account sales and payments is at the bottom of each register closure summary report.
For example, a layby sale for a product with a price of $1000, but a deposit of only $100, appears in your sales history like this:
In the register closure, this will appear as a sale of $1000, with a payment of $100 applied against it.
When this register closure gets sent through to Xero, it should come through as a reconciled Accounts receivable invoice. Payments received must balance against sales taken to show a total invoice value of $0. Retail POS payments are then reconciled against any money received via your bank feeds or cash entries.
In the example, as you have only paid $100 off a sale with a total of $1000, then the total of the sale items will be divided by the fraction of the payment that was received. This means that the quantity that is recorded on the Xero invoice would be 0.1 of the item valued at 1000, in order to balance the invoice.