Q:

vat number required in Magento-2 checkout

I enabled the vat field from admin panel and now i want to make it required during checkout shipping step.
I have followed the steps described here but it is not working.
What is missing from the steps of the above link? Can you suggest how to solve this? 
Thanks in advance

A:

This can be enabled via admin panel:
Stores > Configuration > Customer Configuration > Name and Address Options > Show Tax/VAT Number

The possible options are:

No
Optional
Required

On checkout

Now, other possibilities are :
1
If you navigate to:

Stores > Configuration > Customers > Customer Configuration > (Change
  Scope to correct website/store view) > Create New Account Options >
  Show VAT Number on Storefront
Change dropdown to Yes.

You'll then have to set up your tax classes/tax rules/customer groups and then in the above section you can assign the correct values to the groups. 

http://docs.magento.com/m2/ce/user_guide/tax/vat-validation-configure.html
2 From Database
UPDATE `eav_attribute` SET `is_required` = '1' WHERE `eav_attribute`.`attribute_id` = 36;

