card-fee-audit

---
name: card-fee-audit
description: Turns twelve months of merchant statements and your card processing agreement into the one number nobody gives you, the effective rate you actually pay on every pound taken by card, split into interchange, scheme fees, your acquirer's margin and the standing charges that never appear in a quoted rate, with a written unblending request ready to send to your acquirer and a dated list of every charge that has no explanation. Use when the statement is three pages of codes, when a rate you were quoted does not match the money leaving the account, or before you speak to any provider about a better deal.
---

# The real cost of taking a card in your venue, in one number and four parts, read off your own statements

You give this twelve consecutive merchant statements, the agreement you signed, and the terminal or card reader invoices. You get back your effective rate month by month, the same rate split into interchange, scheme and processing fees, your acquirer's own margin and the fixed charges that sit outside any rate, a list of every line you are billed for that nobody has ever explained, and a written request for an unblended breakdown that you can send tomorrow. It will not tell you whether your rate is good. There is no published figure for what one independent UK venue pays, so the only comparisons it gives you are against your own past months and your own agreement.

## What it does

1. **Collect twelve consecutive months before reading a single line.** Card costs move with the mix of cards, not only with the price list, so one month proves nothing. Gather the twelve most recent merchant statements, the agreement or terms you signed with the acquirer or the independent sales organisation that sold it to you, every terminal lease or hire invoice, and the bank statements for the account the settlements land in. Note for each month the gross card turnover and the number of transactions. If the acquirer deducts fees daily from settlement rather than billing them monthly, say so now, because the effective rate then has to be built from the bank account rather than from an invoice.

2. **Work out which pricing model you are actually on, because it changes what the rest of the audit can see.** There are two shapes. Blended pricing gives you one rate for everything, and inside that single number the interchange, the scheme fee and the acquirer's margin are invisible. Interchange plus plus shows all three separately on every line. The right to see them separately is yours, not a favour. Article 9(1) of the retained Interchange Fee Regulation says each acquirer "shall offer and charge its payee merchant service charges individually specified for different categories and different brands of payment cards with different interchange fee levels unless payees request the acquirer, in writing, to charge blended merchant service charges". If you are on blended pricing and never asked for it in writing, that is the first finding of the audit.

3. **Send the unblending request in writing, dated, and keep the copy.** Article 9(2) requires acquirers to include in their agreements with payees "individually specified information on the amount of the merchant service charges, interchange fees and scheme fees applicable with respect to each category and brand of payment cards", again unless the payee asks otherwise in writing. Article 12 adds a per transaction duty on the acquirer to give you "the amount of any charges for the card-based payment transaction, indicating separately the merchant service charge and the amount of the interchange fee". Regulation 54 of the Payment Services Regulations 2017 requires the information on each transaction, including "a breakdown of the amounts of such charges", at least once a month on paper or another durable medium, free of charge. Ask for all three by name and by reference. The letter is an output of this skill, not homework left for you.

4. **Separate interchange from everything else, and know exactly where the caps stop.** Interchange is the part that goes to the bank that issued the customer's card, and for UK consumer cards it is capped. Article 3 caps a UK debit card transaction at "0,2 % of the value of the transaction" and Article 4 caps a UK credit card transaction at "0.3% of the value of the transaction". A UK debit or credit card transaction means, under Article 2(4A) and 2(5A), one where "the issuer and the acquirer are both located in the United Kingdom" and "the point of sale is in the United Kingdom". So the caps do not reach a commercial card, defined at Article 2(6) as a card "issued to undertakings or public sector entities or self-employed natural persons which is limited in use for business expenses", and they do not reach a card issued outside the UK. A venue near an airport, a hotel, or anywhere a business lunch gets paid on a company card carries a different mix from a suburban cafe, and that mix explains most of the month to month movement people blame on their provider.

5. **Pull the scheme and processing fees out as their own column, and expect them to be the growing part.** The Payment Systems Regulator's final report on card scheme and processing fees, March 2025, found that "average core fees (as a proportion of transaction value) have increased in real terms by at least 25% between 2017 and 2023", and estimated that "UK businesses pay at least 170 million more, annually, for scheme and processing fees than they did seven years ago". It also found that "acquirers typically pass-through scheme and processing fees in full to merchants". That is why this part of the bill rises while your quoted rate stays exactly where it was, and it is why the column has to exist separately rather than sitting inside a blended percentage where nobody can see it move.

6. **List every charge that is not a percentage of a sale, because that is where a small venue leaks.** Terminal or reader rental, a minimum monthly service charge, a PCI compliance or non compliance fee, an authorisation fee per transaction, a refund fee, a chargeback administration fee, a paper statement fee, a gateway fee, an early termination fee. Each gets a row with its amount, its frequency and the clause of the agreement that allows it. On a venue with a low average transaction value, a fixed authorisation fee of a few pence per sale can cost more over a year than the entire headline percentage, and it is completely invisible to anyone comparing quoted rates.

7. **Compute the effective rate the only way that cannot be argued with.** Total card cost for the month, every part of it including the fixed charges and the terminal rental, divided by gross card turnover for the same month, expressed as a percentage to two decimal places. Then do it again excluding the fixed charges, so the transactional rate and the all in rate sit side by side. Do this for each of the twelve months and record the range. Do not average the twelve and quote the average as your rate. A December and a February look nothing alike in a hospitality business, and the average describes a month you never actually trade.

8. **Name every line you cannot explain, and do not guess at it.** The Payment Systems Regulator found that acquirers themselves struggle here, recording that acquirers told it the billing information they receive "is overly complex and lacks transparency" and that some of the largest acquirers in the UK "need to purchase additional services or consultancy services from the schemes to properly understand their fees and services". If a national acquirer cannot always read its own bill, a restaurant is not failing by being unable to read theirs. An unexplained line becomes a numbered question to the acquirer quoting the statement date and the exact wording of the line, never an assumption about what it might be for.

9. **Hand the arithmetic to Codex once every judgement has already been made by you.** Put the statements, the agreement and your notes in one working folder and run, from that folder:

   ```
   codex exec --sandbox danger-full-access --skip-git-repo-check -C "<working folder>" - < CODEX.md
   ```

   Claude hands over the transcribed statement lines, the card turnover and transaction counts per month, your classification of each charge, and the caps and duties quoted above. Codex returns the monthly fee ledger, the effective rate table, the fixed charge schedule, the unblending request letter and a gaps file. Codex never estimates a missing figure and never decides what a charge is for.

10. **Date the file, then write down the three numbers you will read every month from now on.** Put the build date, the statement period covered and the date each figure was read on the front page. Then name what you will watch: the all in effective rate, the scheme and processing column, and the count of unexplained lines. An audit done once is a document. The same three numbers read every month is the thing that catches a fee increase in the month it happens rather than in the year it happens.

## Then it checks

1. Twelve consecutive months of statements are present, each identified by its period, and any gap is named as a gap rather than interpolated.
2. Every monthly effective rate is that month's total card cost divided by that month's gross card turnover, and both figures are traceable to a named statement line or bank statement line.
3. Every charge on every statement appears in exactly one of four buckets, interchange, scheme and processing, acquirer margin, or fixed and ancillary, and no charge is left unclassified without a numbered row in the gaps file.
4. Every line recorded as UK consumer debit or UK consumer credit carries an interchange figure at or below 0.2 per cent and 0.3 per cent respectively, and any figure above a cap is flagged with its statement line rather than quietly corrected.
5. The file states in one sentence whether the business is on blended or unblended pricing, and where it is blended, whether a written request from the merchant for blending exists.
6. No sentence anywhere in the output states or implies a typical, average or benchmark card rate for a UK hospitality business.

Any check fails: name it, redo that step once. Failed twice: say what is wrong and stop.

## Rules
- Public information only.
- Never invent a fact, a number or a quote.
- Anything sent in someone's name says whose name it is.
- Never state a typical, average or benchmark effective card rate for an independent UK venue. No such figure is published. The percentages that circulate come from providers selling card services or from surveys of large retailers, and an owner who believes a borrowed figure will either accept a bad deal because it looks normal or reject a fair one because it looks high. Your own twelve months and your own signed agreement are the only honest comparisons available.
- Never estimate a missing charge, a missing turnover figure or a missing interchange rate. A month without a statement is a hole in the audit, and a hole filled with a guess produces an effective rate that is wrong in a direction nobody can predict.
- Never recommend a provider and never rank providers. This skill reads what you are paying now. Choosing who you pay it to is the payment-choice skill, and that needs quotations this audit has not seen.
- Never present the twelve month average as the rate. Record the range, the highest month and the lowest month, and say which months those were.
- Never turn a high rate into an instruction to surcharge the customer. Charging a consumer for paying by card is unlawful in most of the situations a venue will meet, and the surcharge-law skill sets out exactly where the line sits.
- This output is a working document prepared for the owner to check against their own statements and agreement, and for their accountant to check before it is used in any negotiation, tax return or claim. It applies published rules and caps to figures you supply. It is not financial advice, it is not a legal opinion on your merchant agreement, and it is not a ruling that any charge on your statement is lawful or unlawful.

## Built from
- Regulation (EU) 2015/751 on interchange fees for card-based payment transactions, Article 3, as it applies in the UK, https://www.legislation.gov.uk/eur/2015/751/article/3, read 23 September 2026: the 0.2 per cent cap on a UK debit card transaction, in step 4.
- Regulation (EU) 2015/751, Article 4 as substituted for the UK with effect from 31 December 2020, https://www.legislation.gov.uk/eur/2015/751/article/4, read 23 September 2026: the 0.3 per cent cap on a UK credit card transaction, in step 4.
- Regulation (EU) 2015/751, Article 2 (definitions), https://www.legislation.gov.uk/eur/2015/751/article/2, read 23 September 2026: commercial card, UK debit card transaction, UK credit card transaction and merchant service charge, in steps 4 and 6.
- Regulation (EU) 2015/751, Article 9 (Unblending), https://www.legislation.gov.uk/eur/2015/751/article/9, read 23 September 2026: the duty to offer individually specified charges unless the merchant asks in writing for blending, in steps 2 and 3.
- Regulation (EU) 2015/751, Article 12 (Information to the payee on individual card-based payment transactions), https://www.legislation.gov.uk/eur/2015/751/article/12, read 23 September 2026: the separate statement of merchant service charge and interchange fee, in step 3.
- The Payment Services Regulations 2017, regulation 54, https://www.legislation.gov.uk/uksi/2017/752/regulation/54, read 23 September 2026: the monthly breakdown of transaction charges on paper or another durable medium, free of charge, in step 3.
- Payment Systems Regulator, "Market review of card scheme and processing fees: Final report" MR22/1.10, https://www.psr.org.uk/media/sogjjvl4/mr22-110-card-sp-fees-mr-final-report-publication-redacted-mar-2025-updated.pdf, March 2025, read 23 September 2026: the 25 per cent real increase in core fees, the 170 million figure, full pass through by acquirers, and the transparency findings, in steps 5 and 8.
- Payment Systems Regulator, "Market review into card-acquiring services: Final report" MR18/1.8, https://www.psr.org.uk/media/p1tlg0iw/psr-card-acquiring-market-review-final-report-november-2021.pdf, November 2021, read 23 September 2026: the pre contract and per transaction information duties on acquirers, and the finding that comparing headline rates can be misleading because of additional fees, in steps 3 and 6.

# card-fee-audit

## You are given
Twelve consecutive monthly merchant statements for one UK hospitality business, transcribed line by line, each line carrying the statement period, the statement date, the description exactly as printed, the quantity or transaction count where shown, the rate where shown and the amount in pounds. The gross card turnover and the transaction count for each of those twelve months, each taken from a named source. The merchant agreement or terms of business with the acquirer or the independent sales organisation, including any schedule of charges and any minimum term. Every terminal lease, card reader hire or gateway invoice covering the same period. The bank statements for the settlement account, where fees are deducted from settlement rather than billed. The owner's classification of every statement line into one of four buckets, `interchange`, `scheme_and_processing`, `acquirer_margin` or `fixed_and_ancillary`, or the value `unclassified` where the owner does not know. The owner's statement of whether the pricing is blended or unblended, and whether a written blending request from the merchant exists. The owner's contact details and the acquirer's correspondence address for the unblending letter. Every judgement call, including what each charge is for, which bucket it belongs in and whether a charge is disputed, has already been made by the owner and is supplied to you.

## Produce
Write into a `./card-fee-audit-output/` folder:

1. `fee-ledger.csv` with these columns in this order: `line_ref`, `statement_period`, `statement_date`, `description_verbatim`, `bucket`, `card_category`, `card_origin`, `basis`, `rate_shown`, `quantity`, `amount_gbp`, `source_document`, `classification_source`. `line_ref` is L001 upward. `bucket` is exactly one of `interchange`, `scheme_and_processing`, `acquirer_margin`, `fixed_and_ancillary`, `unclassified`. `card_category` is exactly one of `consumer_debit`, `consumer_credit`, `commercial`, `not_stated`. `card_origin` is exactly one of `uk`, `non_uk`, `not_stated`. `basis` is exactly one of `percentage_of_value`, `per_transaction`, `per_month`, `one_off`, `not_stated`. `classification_source` is exactly one of `owner classified`, `printed on statement`, `not classified`.
2. `monthly-effective-rate.csv` with columns: `statement_period`, `gross_card_turnover_gbp`, `transaction_count`, `interchange_gbp`, `scheme_and_processing_gbp`, `acquirer_margin_gbp`, `fixed_and_ancillary_gbp`, `unclassified_gbp`, `total_cost_gbp`, `transactional_rate_percent`, `all_in_rate_percent`, `cost_per_transaction_gbp`, `completeness`. `transactional_rate_percent` is total cost excluding `fixed_and_ancillary` divided by gross card turnover, to two decimal places. `all_in_rate_percent` is total cost including every bucket divided by gross card turnover, to two decimal places. `completeness` is exactly one of `complete`, `incomplete`. Any month with a missing statement, a missing turnover figure or any `unclassified` amount is `incomplete` and both rate cells are left empty, never estimated.
3. `rate-range.md` recording, on separate lines and nothing else: the number of complete months; the highest all in rate with its month; the lowest all in rate with its month; the highest transactional rate with its month; the lowest transactional rate with its month; and the number of incomplete months with their periods named. No average is written anywhere in this file.
4. `fixed-charges.csv` with columns: `charge_ref`, `description_verbatim`, `amount_gbp`, `frequency`, `months_charged`, `annual_total_gbp`, `agreement_clause_reference`, `clause_text_verbatim`, `authorised_by_agreement`. `frequency` is exactly one of `monthly`, `quarterly`, `annual`, `per_transaction`, `one_off`. `authorised_by_agreement` is `yes`, `no` or `not stated`, copied from the owner's classification, never inferred from the wording of the charge.
5. `interchange-cap-check.csv` with columns: `line_ref`, `statement_period`, `card_category`, `card_origin`, `rate_shown_percent`, `applicable_cap_percent`, `within_cap`. `applicable_cap_percent` is `0.2` for a line marked `consumer_debit` and `uk`, `0.3` for a line marked `consumer_credit` and `uk`, and the literal text `no cap applies` for any line marked `commercial` or `non_uk`. Where `card_category` or `card_origin` is `not_stated`, `applicable_cap_percent` is the literal text `cannot be tested` and the row is listed in `gaps.md`. `within_cap` is `yes`, `no` or `cannot be tested`.
6. `unblending-request.md` a letter addressed to the acquirer at the supplied address, from the supplied merchant name and merchant identification number, dated with the date you run, asking in numbered points for: individually specified merchant service charges under Article 9(1) of Regulation (EU) 2015/751 as it applies in the UK; the agreement information required by Article 9(2); the per transaction information required by Article 12 showing the merchant service charge and the interchange fee separately; and the monthly breakdown required by regulation 54 of the Payment Services Regulations 2017. It states the merchant does not consent to blended merchant service charges. It contains no figures, no allegations and no deadline that the owner has not supplied.
7. `unexplained-lines.csv` with columns: `line_ref`, `statement_period`, `statement_date`, `description_verbatim`, `amount_gbp`, `times_appeared`, `total_over_period_gbp`, `question_for_acquirer`. `question_for_acquirer` quotes the description verbatim and asks what the charge is for and which clause of the agreement authorises it. It never proposes an answer.
8. `gaps.md` a numbered list of: every missing statement period; every month with no turnover figure; every line left `unclassified`; every line where `card_category` or `card_origin` is `not_stated`; every fixed charge with no agreement clause reference; every interchange line that could not be tested against a cap; and any figure the owner supplied without a source document.

## Rules
- Codex transcribes, classifies from the owner's supplied classification, adds up and compares. It never decides what a charge is for, never assigns a bucket the owner did not assign, never decides whether a charge is fair, and never judges whether the business should change provider.
- Never estimate a cost, a rate, a turnover figure or a transaction count. A missing figure leaves an empty cell and produces a line in `gaps.md`. A month with any missing input is reported as `incomplete`, never as a number.
- Never write an average, a median or a typical rate into any file, and never write any figure described as an industry benchmark, a market rate or what other venues pay. No such figure exists for a single independent UK venue and none is to be recorded.
- Never infer a card category or a card origin from a description. Only the owner's classification, or a category printed on the statement itself, supports a value other than `not_stated`.
- Never treat a rate above a cap as an error to be corrected. Record it, mark `within_cap` as `no`, and list it in `gaps.md` for the owner to raise with the acquirer.
- Never write an allegation, a demand or a threat into `unblending-request.md`, and never insert a figure, a deadline or a legal conclusion the owner did not supply.
- Use British English, GBP written as `GBP` or the pound sign, and DD Month YYYY dates. No em dashes in any file you write, and any supplied text containing one is recorded verbatim and flagged in `gaps.md`.
- Every quoted statement description, agreement clause and merchant name is copied exactly, including its punctuation and capitalisation.
- Every file ends with this line: this is a working document prepared for the owner to check against their own statements and merchant agreement, and for their accountant to check before it is used in any negotiation, tax return or claim. It applies published caps and information duties to figures supplied by the owner and is not a ruling that any charge is lawful, unlawful or fair.

## Return
The absolute path of every file written, the row count of each CSV, the number of complete months and the number of incomplete months, the highest and lowest all in effective rate with the month each belongs to, the highest and lowest transactional rate with its month, the total in each of the four buckets across the whole period, the total of `unclassified` amounts, the count of lines that failed the interchange cap check and the count that could not be tested, the annual total of fixed and ancillary charges, the count of unexplained lines and their combined value, and the `gaps.md` item count.