How to Choose a Cash Drawer for Your POS — RJ11 vs RJ12 Explained 2026
Cash drawers are the hardware component most buyers spend the least time researching — and then ask the most questions about after they've ordered. The RJ11/RJ12 distinction confuses almost everyone encountering it for the first time. The size options seem arbitrary. USB cash drawers exist for some systems but not others.
How Cash Drawers Actually Open
There are two mechanisms, and the one you need depends entirely on your POS setup.
Printer-driven (RJ11/RJ12): The cash drawer connects to your receipt printer via a cable. When your POS software completes a cash sale, it sends a signal to the printer, which passes it to the drawer via the cable. The drawer opens. This is the standard for most retail and hospitality setups — it works without any additional configuration and is supported by every major UK EPOS system.
USB (direct to computer or iPad): The cash drawer connects directly to your POS terminal via USB, without going through the printer. The POS software controls the drawer directly. Less common than printer-driven, but used in some Shopify POS and Square configurations where the setup doesn't include a standalone printer.
Wireless (via Bluetooth or network): Some advanced cash drawers support wireless triggers. Relevant for complex multi-till setups. Overkill for most small business applications.
RJ11 vs RJ12 — The Question Everyone Asks
RJ11 and RJ12 look identical. They use the same physical connector housing — the same rectangular plug you'd recognise from a telephone socket. The difference is internal: RJ12 uses all six positions in the connector; RJ11 uses only four.
In practice: most UK cash drawers and most receipt printers use RJ11. The Capture automatic flip-top cash drawer and Storekit automatic medium cash drawer both use RJ11 connections and are compatible with Star TSP143, Epson TM-M30, and Star mPOP printers.
The practical implication: if your drawer cable is RJ11 and your printer port is labelled RJ11 (or DK on Star models), they're compatible. If there's a mismatch — an RJ12 cable on an RJ11 port — it physically fits (the connectors are the same housing) but the pin alignment may not work. When in doubt, check both printer documentation and drawer documentation before ordering.
How to Size a Cash Drawer
Cash drawer sizes are measured in inches, referring to the width:
16" (small): Appropriate for lower cash volumes — perhaps 20–30 cash transactions per day — and tight counter positions. Fewer coin and note slots; smaller form factor.
18" (standard): The most common specification for UK retail and hospitality. Enough compartments for a normal float, suitable for moderate to high cash transaction volumes. This is the right default choice for most setups.
24" (large): High-volume cash retail — supermarkets, market stalls, cash-heavy hospitality environments. More compartments, larger coin tray, heavier build.
Most cafés, independent retailers, and restaurant front-of-house setups use an 18" drawer. If you're uncertain, 18" is the correct specification.
Recommended Models
Capture Automatic Flip-Top Cash Drawer
RJ11 connection, compatible with Star TSP143 and Epson TM-M30 series printers, 18" standard size. Clean build quality for the price.
Storekit Automatic Medium Cash Drawer
The Storekit automatic medium cash drawer is the standard-size drawer with clean design and reliable mechanism. Well-suited to café and boutique retail setups where aesthetics matter alongside function.
Both drawers are available from Commandear's cash drawer collection.
Connecting a Cash Drawer to Your POS System
Step 1: Connect the drawer's RJ11 cable to the cash drawer port on your receipt printer. On Star printers, this port is labelled "DK." On Epson printers, it's typically labelled "DM" or with a cash drawer symbol.
Step 2: In your POS software, enable cash drawer opening on cash sale completion. In Shopify POS: Settings → Hardware → Cash Drawers → Add cash drawer → Printer-driven. Select your connected printer.
Step 3: Process a test cash transaction. The drawer should open automatically.
If the drawer doesn't open: check the cable is fully seated at both ends. Check in POS settings that "Open cash drawer on sale" is enabled. Check the cable is in the DK/DM port — not accidentally in the other RJ11 ports some printers have for daisy-chaining.
Cash Drawer Compatibility by POS System
Shopify POS: Works with printer-driven RJ11 drawers connected to Star or Epson printers. See the Shopify POS hardware guide.
Lightspeed: Standard RJ11 cash drawer connection through the receipt printer. See the Lightspeed starter kit.
Loyverse: RJ11 cash drawer works through the printer. The Loyverse starter kit includes compatible hardware.
PayPal: PayPal supports cash drawers through the printer or direct USB connection depending on your hardware setup. See the PayPal hardware collection.
SumUp: The SumUp EPOS kit is configured for SumUp-compatible hardware setups.
Frequently Asked Questions
What's the difference between RJ11 and RJ12 cash drawers?
The connectors look identical — same physical housing. RJ12 uses all six pins; RJ11 uses four. Most UK retail and hospitality cash drawers and receipt printers use RJ11. Confirm before ordering if you're unsure.
Can I use a USB cash drawer with Shopify POS?
Shopify POS supports USB cash drawers in some configurations. The more common setup is a printer-driven drawer — the printer handles the trigger signal. Check Shopify's hardware page for current USB drawer support.
Why isn't my cash drawer opening?
Most common causes: cable not fully seated, wrong port on the printer (check for DK/DM marking), or POS setting for cash drawer not enabled. Check each in that order.
What size cash drawer do I need?
18" is the standard for most UK retail and hospitality setups. 16" for tight counters or very low cash volume. 24" for high-volume cash operations.
Do all receipt printers work with cash drawers?
Most commercial receipt printers include an RJ11 cash drawer port (DK port on Star models). Budget or consumer-grade printers may not. Star TSP143IV, Epson TM-M30III, and Star mPOP all include cash drawer connectivity.
Shop Cash Drawers
Browse the full cash drawer collection at Commandear — flip-top, standard, and multiple sizes. Pair with a receipt printer and iPad stand for a complete setup. Questions? Contact us.