Citizen CT-S310II software download
Select the OS and component for your application on Citizen’s page.
Identify the interface before installing
CT-S310II is a direct thermal receipt printer. Citizen lists USB + serial and USB + Ethernet configurations; the manual's model classification identifies ET as Ethernet + USB (printed page 10). Inspect the full model label and rear connectors. A cash-drawer connector is not a network port. Do not assume a serial unit has Ethernet or Wi-Fi.
It uses thermal receipt paper rather than ink or toner. The manual covers 58-mm and 80-mm rolls; for blank output, check the specified paper, its printable side and loading diagram first (printed page 28).
Choose the component your application needs
The linked support page has CT-S310II selected. On 2026-10-11, its Windows Driver 3.6.1.0 row lists Windows 10/11 and Server 2016/2019. CUPS macOS/Linux, OPOS, JAVA POS and VCOM are separate downloads. Check the selected package's OS and architecture requirements; a utility, SDK or firmware file is not a replacement for the printing component required by your POS application.
CT-S310II not printing: test the printer first
Self-printing without a computer job
Load paper, hold FEED while turning on the power, keep holding for about one second, then release. The printer outputs its model, version and memory-switch settings (printed page 34). If this fails, investigate media and device status first. If it works, compare the actual cable/port and application before changing software.
Ethernet models: read the current network settings
For a unit fitted with the Ethernet board, a short press of its panel button prints network setup information (printed page 20). Compare the current IP with the computer's selected printer port. Avoid holding the button: the manual also assigns a factory-reset sequence to it. A DHCP address can change after a reset.
POWER/ERROR indications and possible causes
Compare the full indication with Citizen's error explanations, printed page 36 and LED waveform table, page 37. Flashing alone does not identify a driver failure; buzzer behavior also depends on memory settings.
| Indication or symptom | First check | Help |
|---|---|---|
| ERROR stays lit; roll empty | Load the correct paper roll. | Paper loading |
| Cover open; ERROR lit or flashing | Close the cover securely after checking the paper. Opening during printing gives a different indication from standby. | Cover indication |
| Cutter locked; ERROR flashing | Use the illustrated cutter procedure. Do not force the cover or touch the blade; contact Citizen if it cannot retract. | Cutter procedure pp. 32–33 |
| Hot print head; ERROR flashing | Pause for the head to cool; printing resumes automatically after cooling. Do not touch the hot head. | Head-temperature guidance |
| Self-print works; computer/POS fails | Match CT-S310II, the installed interface, the application component and current OS package. | This model driver guide |
| Ethernet job goes to an old address | Compare the board report and the computer printer port before reinstalling software. | Ethernet board guide |
Common computer checks: inspect the selected printer, paused queue and first failed job. If a Windows test prints but only the POS app fails, check its OPOS/JAVA POS/VCOM or ordinary printer configuration. For memory, voltage or system error patterns, use the official table and service guidance.