Abstract: A microcomputerized, miniature postage meter comprises an ink jet printing device adapted to project ink droplets onto a document. A microcomputer, which performs the control and data processing functions of the meter, includes a logic circuit programmed to actuate the ink jet printing device to project ink droplets on the document in a postage indicia forming pattern. In the preferred form of the postage meter, the ink jet printing device is mounted to be moved in close operative proximity relative to the document and the microcomputer is programmed to sequentially actuate the printing device during this relative movement. The movement of the printing device relative to the document is detected by an encoded rotating wheel mounted on the lower contact surface of the printing device. The rotating wheel is coupled to an interrupter disc means which is adapted to provide signal pulses for coordinating the proper time for actuation of the printing device.