Add Legal Number for North American Banking & Financials

This module adds a new field called Legal ID on the partner (customer, vendor or company) form. It is placed on the Accounting tab, right after the fiscal position field, and shows the placeholder "EIN / SSN / BN" so users know what to enter.

When a user types a value in this field, Odoo automatically checks it against three North American formats: - US Employer Identification Number (EIN) - US Social Security Number (SSN) - Canadian Business Number (BN)

If the value matches at least one of these formats, it is accepted. If it does not match any of them, Odoo blocks the save and shows an error message saying the value is not a valid EIN, SSN or Canadian Business Number. Leaving the field empty is allowed.

The module works by extending the partner model (res.partner) with a reusable mixin model (countinghouse.legal_id_number) that holds the field and the validation rule. It depends on the Accounting app (account) because the field is added to the accounting-related partner form view. No new menus, reports or scheduled actions are created; the change is limited to the partner form and its validation behaviour.