What is an authorisation fee on a card machine?

Updated September 2026

An authorisation fee is a small fixed charge, usually a few pence, applied every time your card machine contacts the card network to approve a transaction. It sits on top of your percentage rate, and because it is charged per transaction rather than per pound, it hits businesses with lots of small sales hardest.

The fee covers the authorisation message itself, which is why it can apply even when a transaction is declined or later refunded. Not every provider charges one separately; some roll it into the headline rate, which is one reason two quotes with different shapes are hard to compare on the rate alone.

How much does an authorisation fee add to my costs?

The arithmetic is simple and worth doing on your own numbers. Take a coffee shop processing 3,000 card transactions a month at an average of £4 each. A 2p authorisation fee adds £60 a month — which on £12,000 of card turnover is an extra 0.5% on top of the quoted percentage rate. The same 2p fee on a furniture shop doing 100 transactions at £400 each adds £2 a month, effectively nothing.

That is the whole story of authorisation fees: identical fee, completely different impact, decided by your average transaction value. Low-ticket, high-volume businesses (cafes, bakeries, convenience stores, pubs) should always ask about per-transaction charges before comparing percentage rates.

Why the fee exists at all, and why it is not capped

Every card payment triggers a message to the customer's bank asking whether the money is there. That message costs the provider a fraction of a penny to send, and the authorisation fee is how the cost is passed on. It is a real cost, which is why some providers itemise it, and it is small enough per message that some providers absorb it into the percentage instead.

What it is not is regulated. The Interchange Fee Regulation caps one component of the cost of a card payment, the interchange paid to the card issuer, at 0.2 percent for UK consumer debit cards and 0.3 percent for UK consumer credit cards. Nothing else is capped: not the acquirer margin, not the card scheme fees, and not the authorisation fee. That is why a 2p charge at one provider is 5p at another with no explanation offered and none required.

The practical consequence is that a per-transaction fee is negotiable in a way the interchange floor is not. A business whose transaction count has grown since it signed is asking for a change to an uncapped, provider-set charge, which is a much easier conversation than asking for a lower percentage.

What it costs at different average sale values

The same 2p charge behaves like a completely different product depending on what a typical sale is worth. Expressed as a percentage of turnover, 2p on a £4 sale is 0.50 percent, on an £8 sale 0.25 percent, on a £15 sale 0.13 percent and on a £40 sale 0.05 percent. A 5p charge is two and a half times each of those figures: 1.25 percent on a £4 sale, and still 0.13 percent on a £40 one.

Put that against a headline rate and the arithmetic gets uncomfortable for low-ticket trades. A bakery quoted 1.60 percent with a 5p authorisation fee, taking an average of £4, is really paying about 2.85 percent. The same contract in a restaurant averaging £40 is paying about 1.73 percent. Neither business was misquoted. One of them simply bought a pricing shape that does not suit it.

That is the whole argument for asking about per-transaction charges before comparing percentages, and for doing the sum on your own count rather than on an example. A thousand transactions a month at 3p is £30; ten thousand at 3p is £300, and £300 a month is a part-time wage.

How do I find out what I am being charged?

Look at one monthly statement for a line described as authorisation fees, auth fees, or a per-item charge, and check your contract or fee schedule for a pence-per-transaction figure alongside the percentage. If the statement is unclear, ask the provider directly in writing to confirm every per-transaction charge on the account. Then divide your total monthly charges by your card turnover (the effective rate) which captures authorisation fees and everything else in one comparable number.

Frequently asked questions

Is an authorisation fee charged on declined transactions?

Often, yes — the fee pays for the authorisation attempt, not the sale, so a declined or later-refunded transaction can still incur it. Providers differ on this, so check your own fee schedule or ask the provider to confirm in writing.

Do all card machine providers charge authorisation fees?

No. Some charge a separate pence-per-transaction fee, others build the cost into their headline percentage rate. Neither model is automatically cheaper — a flat rate with no auth fee can suit high-volume small transactions, while separate pricing can suit larger average sales. Compare on your own statement using the effective rate.

Can I negotiate authorisation fees?

Sometimes, particularly if your transaction volumes have grown since you signed. Providers review pricing to keep accounts, and a competitor quote for the same card mix is the strongest thing to have in hand when you ask.

Sources

Checked September 2026. Authorisation fees are set by each provider and are not capped; the figures here are worked examples on your own transaction count, not a quote.

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CapExpand Ltd (Company No. 14433858) is an authorised Dojo partner, not a card machine manufacturer. Card machine pricing and availability are subject to change. Our card machine services are not regulated by the Financial Conduct Authority and fall outside our appointment as an Appointed Representative of White Rose Finance Group Limited, which covers credit broking only.