My card machine is not working: UK crisis runbook
If a UK card terminal stops mid-service, work the 4-step check in order: power, network, software, acquirer status. If the acquirer is down, switch to a sanctioned offline mode (only on Dojo, Adyen or some Worldpay terminals) or take payment by Open Banking link, bank transfer or cash. Avoid writing down card numbers (PCI DSS prohibits it).
The 4-step check, in order
- Power. Battery flat? Plug in for 90 seconds. If the terminal will not power on with mains, the battery may be dead. Most modern UK terminals run from mains alone.
- Network. If the terminal shows "no signal", toggle 4G and WiFi separately. Dojo Go, Stripe Reader S700, PAX A920 Pro and the SumUp Solo all carry 4G SIMs that should take over when WiFi drops. If both are down, no transaction will authorise.
- Software. Reboot. Hold the power button for 10 seconds, wait for shutdown, restart. This clears 70% of intermittent terminal faults.
- Acquirer status. Check on a phone, not the terminal. Each major UK acquirer publishes a status page (linked below). If the acquirer is down, no terminal-side fix will help.
Acquirer status pages and UK support numbers
| Acquirer | UK support phone | Hours | Status page |
|---|---|---|---|
| Dojo | 0800 044 3550 | Tech: 8am-11pm, 7 days | status.dojo.tech |
| SumUp | 020 3510 0160 | Mon-Fri 8am-7pm, weekends 8am-5pm | status.sumup.com |
| Square | 0800 098 8008 | Mon-Fri 9am-5pm (24/7 on Plus plans) | issquareup.com |
| PayPal Zettle | 020 3467 8316 | Mon-Fri 8.30am-5.30pm | paypal-status.com |
| Stripe | In-dashboard request only (no public phone) | Chat 24/7 | status.stripe.com |
Phone numbers verified against each acquirer's official UK contact pages. Last checked May 2026.
Offline (store and forward) mode by acquirer
Store and forward queues transactions on the terminal and forwards them when connectivity returns. The transaction is not authorised in real time, so you carry the chargeback liability if the issuer later declines.
| Acquirer / terminal | Offline mode? | Notes |
|---|---|---|
| Dojo Go | Limited | Store-and-forward available on enterprise contracts. Default Go account is online-only. |
| SumUp Solo | No | Online auth required. Use SumUp Payment Links by SMS as fallback. |
| Zettle Reader 2 | No | Online auth required. PayPal invoice link is the official fallback. |
| Square Terminal | Yes (Offline Mode) | 24-hour offline window, $/£ limit per transaction. Merchant carries chargeback liability. |
| Stripe Reader S700 | Yes (Offline Payments, beta in UK) | Configurable in Stripe Terminal SDK. Liability sits with the merchant. |
| Adyen | Yes (Store and Forward) | Documented offline flow with merchant-side liability rules. |
| Worldpay terminals | Varies by hardware | Older Verifone and Ingenico estate carries floor-limit offline routing. Newer PAX deployments often do not. |
Manual imprinter and paper-receipt fallback
Manual imprinters (zip-zap machines) capture the embossed PAN, expiry and merchant data onto a multi-part voucher. The merchant then submits the paper voucher to the acquirer through a paper route for processing. Two practical issues in 2026:
- Most UK-issued cards are no longer embossed (flat-printed), so the imprinter cannot capture the PAN.
- Paper-route processing windows have shrunk; some acquirers no longer accept manual vouchers at all.
If you genuinely need a paper fallback, pre-confirm with your acquirer in writing and store a current voucher pad. Most UK SMBs in 2026 are better served by an Open Banking link or a contactless mobile wallet on a back-up phone.
Chargeback risk for offline transactions
Mastercard and Visa scheme rules place liability for unauthorised offline transactions on the merchant. If the issuer later declines (insufficient funds, lost or stolen, fraud block), you do not recover the funds. Practical guidance:
- Offline-mode transactions for known regulars only, never strangers.
- Cap individual offline transactions at a level you can afford to lose.
- Submit queued offline transactions within 24 hours; older transactions decline more often.
- Tell the customer the receipt is "pending authorisation", it is.
If your acquirer is the problem, switch
Repeated outages with the same acquirer are a signal. Our switch guides cover the practical exit routes by current provider. Dojo, Square and SumUp are the most-cited destinations for UK SMBs leaving legacy estates.
Frequently asked questions
My card machine has stopped working in the middle of service. What is the very first thing to do?
Check the acquirer's status page on a phone. If their network is down, no troubleshooting on your terminal will fix it. SumUp, Square, Stripe, Dojo and Zettle all publish public status pages. If status is green, move to the 4-step terminal check: power, connection, software, app login.
Should I switch to offline (store and forward) mode while I wait?
Only if your acquirer offers it and you accept the chargeback risk. Offline transactions are not authorised in real time, so a card that is later declined or disputed leaves you fully liable. Dojo, Adyen and some Worldpay terminals support store and forward. SumUp, Zettle, Square and Stripe Tap to Pay generally do not.
Is it legal to write down a card number and process it later?
No. PCI DSS forbids writing or storing the full PAN, expiry and CVV. The only legitimate paper fallback is a manual imprinter (zip-zap), which captures the embossed PAN onto a multi-part voucher and is then processed by your acquirer through a paper route. Most modern UK cards are no longer embossed, so this fallback is largely cosmetic in 2026.
Can I just take cash and bank transfer instead?
Yes, both are legal and have no chargeback risk. Open Banking links sent by SMS (e.g. SumUp Payment Links, Stripe Payment Links, Tide invoice links) are an authenticated bank-to-bank pull and clear in seconds. This is the lowest-risk fallback in 2026.
My terminal says "no signal" but the WiFi is fine. What now?
Modern UK terminals (Dojo Go, Stripe Reader S700, PAX A920 Pro) ship with a 4G SIM that takes priority over WiFi. Toggle WiFi off on the terminal, or move within line of sight of the router. If both 4G and WiFi fail, the terminal cannot authorise.
How long should I wait before calling support?
Run the 4-step check first (power, connection, software, app login), that is 5 minutes. If still down, call. SumUp answers 8am-7pm weekdays, Square 9-5 weekdays, Dojo technical support 8am-11pm seven days. Stripe is chat-only.
My acquirer's status page says everything is green but I still cannot take payments. Why?
Status pages aggregate; small-region or single-merchant outages can be invisible. Try a £0.01 test transaction on your own card. If it declines with an acquirer-side code (e.g. 05, 14, 51, 91), the issue is upstream of the status page and you need to call.
Are chargebacks more likely on offline transactions?
Materially yes. An offline transaction is not authorised in real time, so the acquirer cannot confirm funds, fraud flags or 3DS. If the issuer later declines, you eat the loss. Mastercard and Visa rules treat offline transactions at the merchant's liability. Limit offline mode to known customers or low-ticket items only.
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Oliver leads AcceptCard's editorial and comparison research. With a background in UK commercial finance, he oversees provider analysis, rate verification, and industry reporting across all verticals.
Last reviewed: 7 May 2026