It is important to remove all negative space around your design. If it is not removed, the negative space will be included in the image when it is sent through the artwork processing system.
In this example, the seller wanted a 2" drop from the bottom of the collar to the top of their design. The print resulted in an over 3" drop from the collar. Why?
The dark grey area is the negative space on the customer’s artwork.
The best practice is to crop the negative space from the artwork, leaving a few pixels wide on all sides.
Notice the difference in height when the negative space isn't removed (left) with the design with the negative space removed (right).
The corrected artwork with no negative space included in the mock-up resulted in a 2” drop from the collar as expected from the mock-up whereas the original had an additional 1.25" drop from the collar.