Sale Order Amount to Invoice

This module gives sales users a quick view of how much of a sales order has not yet been invoiced, without opening the related invoices.

On the sales order form, a bold "Amount To Invoice" line is added just below the tax totals block. It shows a read-only monetary value in the order currency, so users can see at a glance the untaxed amount still to be billed.

In the quotations list and the sales orders list, a new optional column named "To Invoice" is added next to the invoice status. The column is hidden by default, so users must enable it through the optional columns selector. It only appears for orders whose state is 'sale' (confirmed sales orders, not draft quotations), and it is summed at the bottom of the list so the total to invoice across the visible orders is shown.

The value is computed automatically from the order lines: the untaxed amount to invoice of each line is summed per order. Because the field is stored, the figure is saved on the order and kept up to date when the related order lines change. No new menus, buttons, emails or scheduled actions are added; the module only extends the existing sale.order screens and the sale.order model.