If the "Pay" button is still showing after the invoice is fully paid, it's likely because the invoice isn't properly marked as Paid. Please check the residual amount—it should be 0.00. Sometimes, even if the payment is done, it's not fully reconciled with the invoice. Also, if you're using any custom code or modules, they might affect the visibility of the button. In standard Odoo, once an invoice is fully paid and reconciled, the "Pay" button should disappear automatically.

Hi,

In Odoo, the visibility of the "Pay" button on a customer invoice is controlled in the form view by conditions that check the invoice's state and sometimes its residual amount (amount_residual).

What you’re seeing in Odoo 18 on-premise sounds like either:

• A view condition regression in the new version, or
• The amount_residual not being computed to 0.0 because of rounding or partial reconciliation issues.

To fix this issue, follow the method below.

1- Change the visibility attribute of the button from UI as,

2- Through code.

 Try the code below in your custom module.

<xpath expr="//button[@name='action_register_payment']" position="attributes">
    <attribute name="invisible">(state != 'posted' or payment_state not in ('not_paid', 'partial', 'in_payment')</attribute>
</xpath>

Hope it helps