How long has it been doing this?
Let me guess. You like to have a really full gas tank. You have a tendency to fill the tank right to the top. You don't like to read that boring owner's manual that tells you not to top off the tank once the nozzle clicks off the first time. You also did not notice a label somewhere on your car telling you not to top off the tank.
(Note, the above may have been the work of a prior owner)
Second guess, the anti-spill valve (That may not be the correct name) may be stuck.
The first one is fixed by changing fill habits, is it really worth the trouble to get two more miles out of a fill? And having the dealer or mechanic replace the damaged part(s). The second you may be able to fix if you can see a ball blocking the vent that you can free it up so it moves properly again.