What are the minimal criteria to satisfy a libel complaint?

If someone makes an untrue statement to my employer about my personal/financial affairs and then further lies about my professional history, does that satisfy the necessary criteria to file a libel complaint? Or does actual harm have to come to me before I have a legitimate cause to address this issue?

I should further specify that this person is not, nor has ever been a personal friend. Neither have I ever had any professional dealing with him in the past. However, currently, his company provides services to my company and I am the project leader.

Our “acquintance” is peripheral in that he is a friend of my ex.

IANAL etc. and since this is regarding an actual situation you’re unlikely to get specific advice, but here is a good definition. If this was a spoken declaration it’s not libel, but slander.