In Pakistan, we have unique set fo tax fields which we call them as NTN # and STRN #.
I have custom script in regional module which will update the fields when someonce select Pakistan as region.
These fields will be added to all docTypes which contains tax feilds such as supplier & customer.
Check how custom fields are added automatically when a country is selected
Regional module: https://github.com/frappe/erpnext/tree/develop/erpnext/regional
Setup code: https://github.com/frappe/erpnext/blob/develop/erpnext/regional/india/setup.py
@rmehta I have already prepared regional module and is working at my end. Now I would like to push it to main branch so every one in this region get’s benefited.
This is probably what you seek https://github.com/frappe/erpnext/wiki/Contribution-Guidelines
That link is referenced here [Oct 2018] Module Maintainers