Abstract: The present disclosure provides universal payment module systems and methods for mobile computing devices that include a universal payment module and an associated adapter device for coupling the universal payment module to any of a plurality of mobile computing devices. The present disclosure utilizes a common payment module which can interface multiple mobile computers with differing form factors via a snap-on sled. Advantageously, the present invention allows the leveraging of one payment module for many mobile computers. The single payment module includes various special payment security mechanisms via mechanical, electrical, and software mechanisms. The present disclosure enables design, standardization, and production of one single common, universal payment module for a plurality of mobile computer devices instead of one specific payment module for each form factor of the plurality of mobile computer devices.