Networking for Tills, Card Terminals, and QR Payments

In shops, restaurants, and pharmacies today, almost no transaction avoids the internet. The till app syncs stock to the cloud, the card terminal contacts the bank, QR payments wait for a notification, and delivery-app orders arrive on a tablet.

When that connection stutters, the queue stops. So the network for payments needs treating differently from the Wi-Fi handed out to customers.

Keep it apart from customer Wi-Fi

This is the first rule and the one most often broken. Two reasons:

• Speed at busy times. When the shop is full, dozens of customer phones compete with the till. That is exactly when most transactions happen.
• Security. Unknown devices on the same network as the till computer are an unnecessary risk. Transaction data and the till app's account must not be reachable from a customer's phone.

The simplest way is the router's guest network feature: the till, card terminals, order tablets, receipt printer, and admin computer sit on the staff network; customers on the guest network with client isolation on. How to do it is in the guide to separating guest networks.

For larger shops or those with several access points, a cleaner separation uses VLANs: each Wi-Fi name (SSID) is mapped to its own VLAN, for example one for tills and payments, one for staff, one for customers, and the till's cable port is placed in the till VLAN. The router is then set so the customer VLAN can reach only the internet, not the other VLANs. The concept is explained in the guide to what a VLAN is.

Cable, Wi-Fi, or SIM

Payment devices can connect in several ways. Each has its place:

The calmest pattern: devices that don't move use cable, devices that move use staff Wi-Fi, and terminals that support a SIM get an active one as a second path. Make sure the Wi-Fi signal is strong across the whole service area, not just near the till. General advice on shop Wi-Fi is in the guide to Wi-Fi for retail shops and convenience stores.

When the card terminal fails at peak hours

Many shops report the same pattern: smooth in the morning, then the terminal or till app starts failing just as the queue gets long. The cause can usually be traced:

Clashing or exhausted IP addresses are covered in the guide to local IPs and DHCP, and prioritising traffic in the guide to bandwidth priority.

A plan for when the internet goes down

The shop's internet will go down one day, a provider fault, a cut cable, or a power cut. What matters is what happens next:

• A dual-WAN router. A router with two connections, such as fibre and a mobile modem, can switch automatically to the second when the first fails. The options are in the guide to backup internet for businesses.
• A hotspot from a dedicated shop phone. Cheaper, but manual. Keep the phone charged, and join the till devices to that hotspot in advance so nobody has to type a password in a panic.
• A SIM in the card terminal. If supported, an active SIM is a second path that doesn't depend on the shop router.
• A small UPS for the router and ONT, so a flicker of power doesn't cut the connection for several minutes, see the guide to a UPS for your router.
• The till app's offline mode. Check whether your app can record sales without internet and sync later. Train staff on it before it is needed.

QR payments left "hanging"

The tensest moment at a till is a customer who has paid by QR while the till screen shows nothing. The cause is often on the shop's side: the notification didn't arrive because the connection stalled.

Set a simple procedure: never ask a customer to pay again before checking the transaction history in the merchant app. A customer charged twice remembers it far longer than a slightly longer queue.

Basic security

The payment card industry has its own security standard, PCI DSS, which includes many of the practices below. The exact obligations for your shop are usually set by your bank or terminal provider, so ask them. Regardless, these habits are worth adopting in even the smallest shop:

• Customers are never given access to the till network, not even "just for a moment".
• The staff network password is not given to customers or posted near the till.
• The admin passwords on the router and other devices are not the defaults, and remote management from the internet is off. The steps are in the guide to securing a router.
• Router firmware and till app updates are installed.
• The till computer is used only as a till, not for watching videos or installing random apps.
• Till app accounts are not shared; each staff member has their own if the app supports it.
• The staff network password is changed when an employee leaves.
• Card terminals get a quick daily look: still the same unit, no overlays or foreign devices attached.

Checklist

• The till network is separate from the customer network, with client isolation on the guest network.
• The till computer and receipt printer are cabled.
• Till devices have fixed IP addresses or DHCP reservations.
• The guest network is speed-limited, till devices are prioritised.
• There is a backup path: dual-WAN, a shop hotspot, or a SIM in the terminal.
• The router and ONT are on a UPS.
• Staff know how to use offline mode and the hanging-QR procedure.
• The bank's merchant helpline and the internet provider's number are posted near the till.

Common mistakes

• One Wi-Fi for everything. Fine when quiet, failing exactly when busy.
• Giving customers the till password because the guest Wi-Fi is playing up.
• Keeping a backup SIM whose validity has lapsed. The backup is found to be dead only when it is needed.
• Asking for payment again before checking the transaction history.

In short

Keep the payment network apart from customer Wi-Fi, cable devices that don't move, and prepare backups before you need them: a second connection, a SIM in the terminal, a UPS, and offline mode. When terminals fail at peak hours, check the customer network first. For a QR payment that doesn't show up, check the history before asking the customer to pay again.

Frequently asked questions