Purchase Invoice Plan - Retention

This module connects two existing features: purchase invoice plans (splitting a purchase order into several invoices) and payment retention (withholding part of a payment).

On a purchase order form, when an invoice plan exists, a small block appears next to the invoice plan lines. It is only visible to users who belong to the payment retention group. There the buyer chooses whether the retention is expressed as a percentage or as an amount, and enters the corresponding value.

When invoices are created from the purchase order, these two values are copied onto the invoice, but only if the order actually uses an invoice plan. The retention is described as a suggestion: during payment the user can still ignore it.

• Adds two fields on purchase.order: a retention type (percent or amount) and a retention value.
• Shows them on the purchase order form, beside the invoice plan lines, hidden when there is no invoice plan and restricted to the retention user group.
• Passes the values to the invoice when the order is invoiced through an invoice plan.

The module installs automatically when both dependencies are present. It does not add menus, reports, scheduled jobs or extra checks; it only adds the fields, the form block and the copy of the values to the invoice.