I'm working in Germany. My company usually gives a 13th salary to its employees, divided in 2 parts (one half in June, and the second in December). It's not technically a 13th salary, since it's not on my contract and they often stated that this is a voluntary bonus that they give.
Now, since I've announced my resignation (they haven't stated the reason YET but that is the only explanation), they are not going to give it to me, even though I've received it in the past and I qualify for it (I've worked the whole year, and I'm going to be employed until the end of December).
Are they allowed to do that? I know it's a voluntary thing, but if my colleagues are receiving it, is my company allowed to just exclude me from it?