This paper proposes a transparent logic circuit for radio frequency identification (RFID) tags in amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) technology. The RFID logic circuit generates 16-bit code programmed in read-only memory. All circuits are implemented in a pseudo-CMOS logic style using transparent a-IGZO TFTs. The transmittance degradation due to the transparent RFID logic chip is 2.5% to 8% in a 300-nm to 800-nm wavelength. The RFID logic chip generates Manchester-encoded 16-bit data with a 3.2-kHz clock frequency and consumes 170 ${mu}W$ at $V_{DD}=6$ V. It employs 222 transistors and occupies a chip area of 5.85 $mm^2$.