Nifone is a small and simple program, totally free and in English, that does not even require installation.
It is a small office utility that allows you to quickly obtain the letter that corresponds to each ID. For this, the Nifone user must only enter the number of the DNI from which he wants to obtain the letter, and then he will provide the letter assigned to said DNI.
In short, Nifone is a very basic, simple and even austere tool, but it will be very useful for you when you need to obtain this information from the NIF (because it is often missing from the administrative forms that are usually received).
You can free download Nifone 32, 64 bit and safe install the latest trial or new full version for Windows 10 from the official site.