After Install:

Natively, odoo does not have the relationship of sales and invoices, for this reason we will have to execute a planned action for all those invoices created before the installation of this module.

Step 1:

Enter the "Settings" module, then in developer mode enter the "Technical" menu item, looking for the "Scheduled Actions" option.

Step 2:

Look for the record called "Mapping Sale Invoice", when you are inside click on the "Run Manually" button.

This will execute a database query to generate sales relationships with their respective invoices, a fundamental process to add advance payments and generate reports.

Step 3:

Add the permission to the users that you want to add advances to sales, (all sales users will be able to observe advances, but not only those with this permission will be able to create advances).

Step 4:

At the sales configuration level, it must be established in which sales state it will be possible to add advances.

How does it work?

From the sale we will have the "Advance Payment" button to be able to add a payment, you will have to establish the amount of your advance and then click on the "Validate" button.

The amount of advance could be:
1. The total amount of the sale if you do not have any payment added previously.
2. The remainder pending from the sum of the amount owed + the amount not billed.

You will be able to add payments with a different customer than your quote without having the problem of not being able to add to the invoice.

When creating an invoice linked to the sale, or having one previously created, we can add the advances by clicking the "Add payment advance" button.