We have a custom module, this modules generates a field called CONTROL when you validate the INOVICE, it uses several fields from the INVOICE, also it uses a field called NIT (an integer field).
First: We need that you modify this module in the following:
--In the partner form we need a field called NIT (char field)
--The NIT field must be used to search the corresponding partner name in Sale Order and Account Invoice
Second: The CONTROL module creates a NIT field(integer) in the Account Invoice, this Nit must be populated with the current NIT field of the partner, the populate must be in an ONCHANGE way so when you change a partner name you see the new NIT number.
Third: The NIT field we use now is a 16 digits number, you need to make some changes to the module, because of the Big Integer problem
First: For each of the POS you need to add a field in the [login to view URL] called INVOICE, this field must select an INVOICE report, this report must be printed in the current POS.
Second: In the POS Customer Search you must be able to search the client with the NIT
number and it must be shown in the POS client list. Also the NIT field must be EDITABLE from the customer edit form.