RE: How to block editing a specific field already filled in
Hello Igor,
This looks like the Vendor Details form. You must have some localisation enabled because I do not have that Fiscal Information FastTab in my demo environment.
You can achieve using Security Privileges or Field Level Security. I would not advise doing this alone for the first time, unless you have time to familiarise yourself with D365 Security objects and can work in a dedicated test environnment.
You will have to determine if there a privilege that address only that pecific field, if so you can copy that privilege into a new privilege and modify it to allow Create and Read (not Update or Delete). You have to be careful not to change existing privileges, duties and roles (duplicate and modify these objects, do not change the standard onea).
Alternatively, you can use Field Level Security. Here is a blog that describes the "how-to" of Field Level Security (bonus: it happens to be use the Vendor Table!). You will want to give create and read access (but not update or delete) :
alexdmeyer.com/.../
Good luck!
