Not handling Company Tax ID field on submission of Sales Invoice for Italian E-Invoicing

[rahib-hassan]

Information about bug

Adding an Issue and not a PR since I am unsure about the legal side.

Issue

In the current implementation of e-invoicing for Italy, the company_tax_id is not being handled properly.
https://github.com/frappe/erpnext/blob/43ce185429ad125d76379e5a98179181627e2d8e/erpnext/regional/italy/utils.py#L264

In the sales_invoice_validate() method, an error is thrown only if both company_tax_id and company_fiscal_code are missing. This allows invoices to proceed if at least one of these fields is set. and in the get_progressive_name_and_number() method, the company_tax_id is accessed without a fallback mechanism, leading to runtime errors if it is not set.

if not doc.company_tax_id and not doc.company_fiscal_code:
	frappe.throw(
		_("Please set either the Tax ID or Fiscal Code on Company '%s'" % doc.company),
		title=_("E-Invoicing Information Missing"),
	)

https://github.com/frappe/erpnext/blob/43ce185429ad125d76379e5a98179181627e2d8e/erpnext/regional/italy/utils.py#L469

company_tax_id = doc.company_tax_id if doc.company_tax_id.startswith("IT") else "IT" + doc.company_tax_id

Steps to Reproduce:

1. Create a company in the Italian regional setup without setting a tax_id but with a fiscal_code.
2. Create a sales invoice for this company.
3. Validation does not raise any error in sales_invoice_validate() since the fiscal_code is set.
4. During submission of the sales invoice it triggers get_progressive_name_and_number() method.
5. A runtime error occurs because company_tax_id is accessed directly without checking its existence.

Suggested Solution

1. Throw an error if company_tax_id is not present during validation.
2. Handle get_progressive_name_and_number() method by including either company_fiscal_code or tax_id

company_tax_id = doc.company_tax_id if doc.company_tax_id and doc.company_tax_id.startswith("IT") else "IT" + (doc.company_tax_id or doc.tax_id)
if not company_tax_id:
    frappe.throw(
        _("Company Tax ID is required to generate the progressive name."),
        title=_("Missing Information")
    )

Module

regional

Version

Frappe Version - Version-15
ERPNext Version - Version-15

Installation method

None

Relevant log output / Stack trace / Full Error Message.