brotherton-erpnext/erpnext/patches/v12_0/create_taxable_value_field.py

import frappe
from frappe.custom.doctype.custom_field.custom_field import create_custom_fields


def execute():
	company = frappe.get_all("Company", filters={"country": "India"})
	if not company:
		return

	custom_fields = {
		"Sales Invoice Item": [
			dict(
				fieldname="taxable_value",
				label="Taxable Value",
				fieldtype="Currency",
				insert_after="base_net_amount",
				hidden=1,
				options="Company:company:default_currency",
				print_hide=1,
			)
		]
	}

	create_custom_fields(custom_fields, update=True)