A trench coat is a versatile coat, but it should be preferred as a casual chic option, But this doesn’t mean you can’t use it in a formal situation. You can use it in formal settings too, as a topcoat for a three-piece formal suit or you can replace a formal suit jacket with a tailored trench coat preferably in earthy tones. So a trench coat is often used in casual situations, and occasionally in formal settings.