On suits, blazers and jackets, there’s a simple style rule: Do button other buttons sometimes or always except the bottom button, whether it’s a three-button or two-button outfit.
The bottom button will bunch up your clothing and make you look rumpled. Button other buttons if they make you feel more comfortable and look more put-together.
Remember this rule: Jackets are designed to NOT use the bottom button. So in a 3 button jacket it goes starting from the top SOMETIMES, ALWAYS, & NEVER and in a 2 button is just ALWAYS & NEVER