If you need to use the white GoPayment card reader with a large case (such as an Otterbox) you may have to remove the case to successfully use the swiper. You can also purchase an audio jack extension to allow the card reader to connect with the large case on. You should not need to use an audio jack extension with the grey GoPayment card reader.
Important: Intuit does not support or warranty the use of an audio jack extension; however, many GoPayment users have reported success using this device with the white GoPayment card reader.
The extension needs to be a 3.5mm 4 conductor plug. It will have 3 colored rings on the metal piece vs. the 2 colored rings on basic headphones. These can be found at Amazon, Ebay, or other web sites and consumer electronics stores.
Sample image of an audio jack extension: