Who This Payment Terminal Comparison Is For
If you run a shop, café, restaurant, market stall, or service business and you accept card payments, the terminal you choose has a direct and ongoing impact on your margins. Most business owners pick the first option they hear about — and end up paying a percentage of every sale, indefinitely, without ever reviewing whether it is the right model for their volume and transaction value.
This comparison focuses on what matters after the hardware arrives: what you actually pay per month, how the pricing model scales as your business grows, and where each platform works best in practice.
Flatpay: The Flat-Fee Model That Rewards Businesses With Higher Transaction Values
Flatpay is a Danish payment company built around a simple premise: businesses should pay a predictable flat monthly fee for payment processing, not a percentage of every sale. Where traditional processors take 1.5–2.5% of each transaction, Flatpay charges a fixed monthly subscription and a small flat fee per transaction — meaning a £500 sale costs the same to process as a £50 one.
This model becomes increasingly advantageous as your average transaction value rises. For restaurants, trades businesses, and retail shops with basket sizes above £30–40, the monthly savings compared to percentage-based processing can be substantial. Flatpay operates across multiple European markets including the UK, Denmark, Sweden, Norway, Finland, Germany, and the Netherlands, and its onboarding is genuinely straightforward — hardware arrives quickly and setup requires no technical knowledge.
The tradeoff is the fixed monthly commitment. For businesses with very low transaction volumes or highly seasonal operations, paying a flat monthly fee regardless of sales activity is less efficient than a pay-per-transaction model. Flatpay makes most sense when card payment volume is consistent and transaction values are meaningful.
SumUp: Best Entry Point for Low-Volume and Mobile Businesses
SumUp is the most accessible card payment option in this group. Its hardware starts at a low upfront cost, there is no monthly fee on the base offering, and the 1.69% per-transaction rate is competitive for businesses just starting to accept cards or processing relatively low monthly volumes.
For market traders, mobile service businesses, and early-stage operators who take cards occasionally rather than constantly, SumUp removes the commitment barrier entirely. You pay when you earn. The app is clean, the hardware is reliable, and the onboarding takes minutes.
Where SumUp becomes expensive is at volume. A business processing £20,000 per month at 1.69% is paying £338 in fees — more than the flat monthly cost of Flatpay at that level. For businesses that have grown past the early stage and are processing consistently, staying on a percentage model is often an unnecessary cost that compounds month over month.
Zettle: Best for Businesses That Want POS Software Alongside Payment Processing
Zettle by PayPal (formerly iZettle) sits at 1.75% per transaction and brings stronger POS software capability than SumUp as a built-in feature. Inventory management, sales reporting, staff accounts, and a proper point-of-sale interface are available without needing third-party integrations — making it a stronger fit for retail and hospitality businesses that need more than a card reader.
The PayPal integration is a genuine advantage for businesses that already use PayPal for online sales — unified reporting across in-person and online transactions simplifies reconciliation. However, as with SumUp, the percentage-based fee model becomes increasingly costly as transaction volumes grow. And for businesses that process PayPal payments less frequently, the PayPal ownership of Zettle adds less meaningful value.
What the True Monthly Cost Actually Looks Like
The most important calculation before choosing a payment terminal is your average monthly card volume. At £5,000 per month, SumUp costs £84.50 in fees and Zettle costs £87.50 — both below Flatpay’s flat monthly rate. At £15,000 per month, SumUp costs £253.50 and Zettle costs £262.50 — both likely above what Flatpay charges. The crossover point varies by plan, but for most businesses consistently processing more than £8,000–10,000 per month in card payments, Flatpay’s model becomes the more cost-effective option.
Final Recommendation by Business Type
Choose Flatpay if you process card payments consistently, have an average transaction value above £30, and want a predictable monthly cost that does not grow with every sale. Choose SumUp if you are starting out, have low or variable transaction volumes, and want no monthly commitment. Choose Zettle if you need integrated POS software alongside payment processing and are already in the PayPal ecosystem.