A collar gap is one of those tricky details that even sartorial perfectionists get wrong from time to time.
It occurs when there is too much space between a man’s suit jacket collar and the dress shirt collar worn beneath.
Collar gap can come from an imperfect fit on the chest or shoulders, incorrect posture or even a neck that is too long for the jacket cut. Signs of a collar gap include the shirt collar fully showing, the suit jacket pulling away from the shirt collar and divots or crinkles in the lines of the jacket’s front or bunching in the back when the wearer moves.
There are ways that a skilled tailor can fix a collar gap:
If the gap is not too bad, a tailor can consider several things including how the shoulders are cut or how the chest fits to determine if the collar can be fixed. In an extreme case, a collar can be removed and recut. But this is not advisable and will likely never result in a perfect looking fit.
So it’s always best to consider the collar gap from the start. A well cut jacket collar should sit naturally at less than half an inch from the shirt collar and there should be no gap either in the back or the sides.