Tax ID or VAT no in documents Ver 6

ERPNext: v6.27.9
Frappe Framework: v6.27.10

I am trying to add Tax ID or Vat number to the sales order and Sales invoice document. The customer field has a field called Tax ID with field name “tax_id”

So in SETUP-> CUSTOM SCRIPTS-> we add this script “cur_frm.add_fetch(“customer”,“tax_id”,“tax_id”);” to Doc type Sales Order.
Then iSETUP->CUSTOM FIELD we add the following
Document
Sales Order
Label
Tax ID
Fieldname
tax_id
Insert After
Custom name
Select the label after which you want to insert new field.
Field Type
DATA

Then you go to quotations and create a sales order but the TAX ID field is not filled in. It is as if the script is not running to transfer the tax_id to the sales order. Even after reloading “clear Cache”.

Please advise

Hello Go to setup / custom scrip select sales invoice as target document and add this line cur_frm.add_fetch(“customer”,“tax_id”,“tax_id”); save reload and clear cache dont use The “” at The bigining and end of code.

I have not used " at the beginning and end of the code. I have attached screen shots.





The Tax id is in the Customer form. This is listed in the documentation as having a field name of tax_id.
I just cannot see why the Tax ID is in the sales order screen but it is empty. The tax_id from the customer form is not transfered. I have the tax_id in the custom field screen showing the type as DATA. Even clearing cache logging out and in then creating a new sales order does not work.
In the customize form you can see the TAX ID line 7

you are right it should work out of the box , try creating a new field at customer label called for example vat as data and add this code cur_frm.add_fetch(“customer”,“vat”,“tax_id”);