Debit card interchange fee cap: the ceiling on your debit traffic, and the routing choice that is legally yours

Somebody asked me last spring why their debit costs looked like their credit costs, and I gave the answer I had given for 2 years without ever opening the regulation. I have read all of it since, which took most of an afternoon and was less painful than expected. The processor routes the payment, the networks price it, and a shop of your size takes what it is given. I believed all 3 clauses. The middle one is wrong for debit, and the last one is wrong as a matter of law, which is an uncomfortable thing to discover in your own words on somebody else's screen. I still find it hard to read that thread without wincing.

Pull a statement first. Do not take my arithmetic on trust, never take a processor's summary as the detail, and find the debit lines yourself, because the whole argument below turns on whether the fee against those lines looks like a flat few cents or like a slice of the basket. If it is a slice, this piece is about money you are leaving with somebody else.

The debit card interchange fee cap is a federal rule with a number in it, and the routing right that sits next to it is the part almost nobody uses. What follows is the ceiling, the choice, and the parts I could not establish.

The ceiling, and what it does to a basket

Regulation II sets the maximum an issuer may receive on a covered debit transaction, and the formula has 2 parts. The rule allows a base component that does not vary with the value of the sale, plus a small percentage on top. The published ceiling is “the maximum permissible base component of 21 cents and 5 basis points of the value of the transaction.”

Five basis points is 0.05 per cent. The regulation gives its own worked example, which is worth reading twice if you have ever been quoted debit pricing as a flat percentage: “For a $39 transaction, the maximum permissible interchange transaction fee is 22.95 cents (21 cents plus 5 basis points of $39).”

Put that against the way most small merchants are billed. A blended rate of 2.6 per cent on a 39 dollar sale is 1.01 dollars. The regulated ceiling on the interchange part of that same sale is 22.95 cents. The gap is not all profit for anybody, because there are network fees and the processor's own margin in there, and I am not claiming the whole difference is recoverable. The point is smaller and harder to argue with: on covered debit, the largest single component of your cost has a legal ceiling of about 23 cents at that basket size.

The base component is the part that changes how you think about small baskets. It does not move with the value of the sale, so a 4 dollar coffee and a 400 dollar order carry the same 21 cents underneath. Percentage pricing hides that completely. A shop selling cheap things at volume is the one paying most dearly for the hiding.

The choice that is legally yours

This is the half I had wrong, and I had it wrong in a way that cost readers money rather than just embarrassing me. The rule requires an issuer to set up every debit card so that each transaction can run on at least 2 unaffiliated networks. Not one network with a backup. Two, and they cannot be siblings.

Then the sentence that matters for a website. The requirement applies “for each geographic area, specific merchant, particular type of merchant, and particular type of transaction for which the issuer's debit card can be used”, and the regulation gives its own example of what a particular type of transaction means: “card-not-present transaction”. Online is named. It is not an oversight that somebody is graciously extending to you.

The rule states it in one line. An issuer must configure each debit card so that “each electronic debit transaction performed with such card can be processed on at least two unaffiliated payment card networks.” Next to that sits a prohibition on inhibiting a merchant's ability to determine routing, and reading those 2 clauses together gives the shape of the whole thing: the issuer has to provide at least 2 roads, and nobody in the chain is allowed to take the choice of road away from the merchant. Whether your processor exposes that choice in a form you can act on is a separate question. That is where the real work is.

Two details that decide whether this applies to you

The first is about business cards. I had assumed the whole regime was consumer protection and that a company debit card sat outside it. The commentary says otherwise in the flattest possible language: the term account “includes accounts held by any person, including consumer accounts … and business accounts”, so the fee limits and the routing rules apply to business-purpose debit cards as well. If you sell to other companies, this is your traffic too.

The second is about small banks. Issuers under the asset threshold are exempt from the fee ceiling, which is why some debit still arrives expensive and lawfully so. But the exemption does not reach the routing rules. The commentary is explicit that cards from exempt programmes are “subject to the requirement that electronic debit transactions made using such cards must be capable of being processed on at least two unaffiliated payment card networks”. So the cheap card may be capped and the expensive card is still routable.

The same ceiling across 3 basket sizes

I ran this on 3 real statements before writing it down, which is the only reason I trust the shape of it. Do this on your own numbers. It takes a minute and it decides the rest, because the same ceiling behaves like a completely different fee depending on what you sell. On a 4 dollar sale it is 21.2 cents, or 5.3 per cent of the basket. On the regulation's own 39 dollar example it is 22.95 cents. On a 400 dollar order it is 41 cents, which is 0.10 per cent.

Read down that column and the design shows itself. The flat 21 cents dominates small baskets and disappears into large ones, which is the whole reason percentage pricing feels fair to one shop and expensive to another. A blended percentage does exactly the reverse, so the merchant selling 4 dollar items is overpaying on percentage pricing and the one selling 400 dollar items is often getting a bargain from it.

Work out which of those 2 shops you are before asking anybody for a better rate, because the conversation is completely different in each case: a shop with a 12 dollar average order is negotiating about the flat 21 cents and the routing that decides whose 21 cents it is, while a shop with a 400 dollar average order is negotiating about the markup and barely notices the ceiling at all. If your average order is 12 dollars, the flat 21 cents is the number that decides your economics, and no amount of negotiating a percentage will touch it.

Who is exempt and why your statement may be lawful anyway

The exemption line is drawn at assets. An issuer that, together with its affiliates, has assets of less than 10 billion dollars is exempt from the interchange fee restrictions, and the commentary says so plainly while working through the sponsored card model. So a card from a small community bank can carry an interchange fee well above 23 cents on that 39 dollar sale and nobody has broken a rule.

That changes the mix, not the ceiling. You do not choose which bank your customer uses, so some share of your debit traffic sits outside the 21 cent cap in every single month. My guess is that most online shops have never seen the split. Statements rarely separate regulated debit from exempt debit. Ask for it by name.

A second exemption covers government-administered programmes and certain reloadable prepaid cards, and it works the same way as the 10 billion dollar one: outside the fee ceiling, inside the 2 network rule. I cannot tell you what share of your traffic that is either, and I have not found a public source that breaks it out by merchant size.

The exempt share is not small in the United States. There are thousands of banks and credit unions under the 10 billion dollar line, and every one of them issues debit cards that sit outside the 21 cent ceiling while staying inside the 2 network rule. So your blended debit cost is a weighted average of capped and uncapped traffic, and the weights are not yours to set.

What I would actually do with a statement

Start by separating debit from credit, which sounds obvious and is the step most merchants skip because their statement does not do it for them. Ask the processor for interchange detail on a month, by card type. If the answer is that they cannot provide it, that answer is itself information about the pricing model you are on.

Look at the shape of the fee, not its size. Regulated debit reads as a flat 21 cents plus a sliver of the basket. Regulated debit should look like a flat few cents plus a sliver. If your debit lines scale smoothly with basket value, you are on a blended rate and the ceiling is being collected by somebody between you and the issuer.

Then ask about routing in writing, because a verbal yes on this subject has cost me a year of believing something that was true only in a shop with a card reader. The phrase that gets a real answer is least cost routing. Ask whether it is on for card-not-present specifically.

An aside that has nothing to do with regulation. This stays unclaimed because 12 cents a sale is small enough to feel unserious, nobody tells that story at a dinner, and a saving that cannot be told as a story sits uncollected for years in a business that is otherwise ruthless about every other cost line. On 40,000 orders it is 4,800 dollars. Right, back to the rules.

Where the ceiling stops being the whole answer

Interchange is not your total cost and I do not want to pretend otherwise. There are network assessments, there is the processor's markup, and on a small account the markup is usually the larger of the 2. A merchant who wins the routing argument and keeps a bad markup has moved a number without moving the total.

There is also a fraud-prevention adjustment in the rule, which lets a qualifying issuer take a little more, provided it maintains policies and procedures reasonably designed to reduce fraud. It is small next to the base component. I mention it because it explains why the ceiling you compute by hand and the number on your statement can differ slightly without anybody breaking a rule.

One more number for the file. The base component has sat at 21 cents since the standard was written, and 5 basis points on a 39 dollar sale is under 2 cents, so almost the whole ceiling is the flat part. Any argument about debit pricing that talks only in percentages is arguing about the smaller half.

What I could not establish

How many small merchants actually have card-not-present routing enabled. I could not find a published figure from the Federal Reserve, the networks or any processor, and the trade press numbers I did find were vendor surveys with the method left out. So I do not know whether I am describing a right that half the market uses or 2 per cent of it.

Whether asking for it changes anything at the smallest end. The rule binds issuers and prohibits inhibiting the merchant, and it does not order your processor to build you a routing switch. I asked 2 payment leads at small shops and got 2 different experiences, one a shrug and one a saving, which is not a dataset.

The detail I keep coming back to is the 21 cents, and my guess is that nobody will reopen it soon. It has not moved since the standard was written, so its real value has been quietly falling for years while every percentage-based fee around it kept pace with prices. I am not sure whether that is a design or an oversight, and I have stopped expecting anybody to say.