You’ve probably wondered what causes the bunching below the collar on your suit jacket or blazer. This phenomenon is called a neck roll and it is directly related to your shoulders. No there’s nothing wrong with you or your shoulders, but if your jackets are constantly having a roll near the neck you probably have square shoulders and are wearing jackets cut for sloped shoulders (like most off-the-rack jackets).
There is a popular assumption that the jacket neck roll is caused by tightness through shoulders/blades which produces a “rippling” effect across the upper back, and divots at the top of the sleeves. While that does exacerbate the issue, the root cause of the problem comes down to uneven shoulder slopes. In rare cases, a collar roll can be blamed on a short neck which causes some excess fabric to “pool” under the collar which is being pushed down.
A good tailor can fix this by removing the collar and recutting the neck hole and front and back panels. What you can expect when working on the shoulders, however, is a difficult and expensive process.
If you feel that this is a constant issue with most or all of your jackets going custom might make sense as it will assure you a jacket properly adjusted for your frame. It’s no secret that fit is the most essential aspect of a jacket and it starts with the shoulders.