Hi,

Try this code:

def action_create_invoice(self):

        self.ensure_one()

        # Create an invoice record with a link to the current Sales Order

        invoice_vals = {

            'service_order_id': self.id,  # Assuming the field name is 'service_order_id'

            # ... other fields for the invoice ...

        }

        # Create the invoice record

        new_invoice = self.env['pma.invoicing'].create(invoice_vals)

        # Return the action to open the created invoice in form view

        return {

            'name': _("Create Invoicing"),

            'res_model': 'pma.invoicing',

            'type': 'ir.actions.act_window',

            'view_mode': 'form',

            'view_type': 'form',

            'res_id': new_invoice.id,  # Open the form view of the newly created invoice

            'target': 'current',

        }

Hope it helps