"Bang" from gas tank

Just about every time I fill my gas tank, I hear a bang from the tank as it reaches its full capacity. My wife has also told me she felt the bang when sitting in the drivers seat(as I was filling). I have read about pressure building in the tank that is suddenly released that could cause the "bang". Any thoughts as to the cause and a possible remedy?

You may have a shallow dent at the bottom of the fuel tank. The weight of the fuel 'pops' the tank to its original shape; and as the fuel is drained from running, the fuel tank returns to its dented shape.

The next time you are filling it, look underneath as someone else fills it, and look/listen for the 'pop'. Also check for loose straps, too.