BUG? Understand why TAX ID field disappears??

[zitu4life]

Hello there

I am trying to understand why tax id has this behavior.

steps reproduced:

1 - Add new client and leave tax id empty
 

2 - After create this client, goo to this client summary page and next to profile tab to edit this client information

3 - Even Full administrator can not insert TAX ID later for client that not had inserted TAX ID on first time that client were added to the system. Does this behavior correct or is it a bug?

PS: even on default blend we have this situation!!

Edited March 3, 2020 by zitu4life
adding PS:

[Kian]

Is Setup > Payments > Tax Configuration enabled? If yes, maybe WHMCS forgot to make Tax ID field conditional in Add New Client page depending on Tax Configuration.

Edited March 3, 2020 by Kian

[brian!]

if you migrated from using a custom field, in your tblconfiguration table, do you still have a value in the TaxVatCustomFieldId value column ?

[zitu4life]

19 minutes ago, Kian said:

Is Setup > Payments > Tax Configuration enabled? If yes, maybe WHMCS forgot to make Tax ID field conditional in Add New Client page depending on Tax Configuration.

Yes. that it!! i have Tax configuration disabled because I use external Accounting software because WHMCS will not be accepted in my country as certified invoices, so  I use WHMCS as management system, but for official invoice I use other software, so that is why i have tax disabled, and now i realized that WHMCS have it linked to that...But I still use WHMCS to store all client information including TAX ID. 
I will try to activated tax on WHMCS and see if it will not cause me issues, because all my products and services are tax included and I can not split it on invoices....usually  government will sum all invoiced amount and apply x% of tax to be paid.

PS: I am not allowed to invoice clients splinting and showing x% tax even on emails send out, that is why i always have TAX disabled.

Interesting is even with TAX ID disabled WHMCS allows you to insert TAX, so that is why it make me think it could be a bug, because sometimes TAX is there and sometimes it is not.

Many thanks