The MCC Problem
Visa classifies card-to-crypto purchases under MCC 6051 — Non-Financial Institutions, which covers foreign currency and money orders. This classification is not a detail. Card issuers can apply blanket blocks at the MCC level, and several major UK banks have enabled or experimented with MCC 6051 blocks for their customers. Unlike iGaming blocks (which are customer-opted-in), some issuer-level crypto blocks have been applied without customer choice.
The classification also means that every card transaction your exchange processes is visible to the card schemes as a crypto purchase. There is no obfuscating this through descriptor management — the MCC is passed in the authorisation request and is scheme-visible regardless of what your billing descriptor says to the cardholder.
Why Mainstream PSPs Won't Onboard You
Stripe, PayPal, Square, Checkout.com, and Adyen all maintain explicit prohibitions on crypto exchange transactions. This is not negotiable and not addressable through compliance documentation. The reasons are layered:
- Elevated chargeback exposure. Price volatility creates a class of dispute unique to crypto — the buyer received exactly what they purchased, but disputes the transaction after the asset declined in value.
- AML/KYC complexity. Mainstream PSPs have standardised risk models. Crypto exchanges operating in multiple jurisdictions with varied KYC obligations fall outside those models in ways that are expensive to underwrite individually.
- Card scheme pressure. Visa and Mastercard have both issued guidance discouraging mainstream acquirers from aggressively growing crypto exchange volume. Specialist acquirers price for the risk; mainstream acquirers prefer to avoid it.
- Regulatory trajectory risk. Acquirers are aware that crypto regulation is rapidly evolving. Exposure to a merchant category whose legal status could change in key jurisdictions is a risk most mainstream acquirers prefer not to carry.
FCA Registration: A Practical Prerequisite
For UK-facing operations, FCA registration under the UK Money Laundering Regulations (MLR 2017) as a cryptoasset business is effectively a prerequisite for card acquiring, not just a regulatory obligation. Most specialist acquirers require proof of FCA registration before opening underwriting. Without it, you are dependent on acquirers operating outside FCA oversight, which tends to mean less stable relationships, less transparent terms, and higher risk of abrupt termination.
FCA registration for cryptoassets is distinct from FCA authorisation. Registration covers AML/CTF obligations; it does not constitute authorisation to conduct regulated financial services. If your exchange also facilitates derivatives trading or securities-linked crypto products, separate FCA authorisation may be required — which significantly affects which acquirers will work with you and on what terms.
The Travel Rule and acquiring
The UK's implementation of the FATF Travel Rule (effective 2023) requires crypto exchanges to collect and transmit originator and beneficiary information on transfers above £1,000. Acquirers who have undergone their own compliance assessments of crypto exchange onboarding increasingly require evidence of Travel Rule compliance as part of due diligence — not just FCA registration.
Velocity Limits and Per-Transaction Caps
Unlike most merchant categories where acquirers approve unlimited transaction values within settlement limits, crypto exchanges operate under specific velocity controls imposed by the acquiring agreement. These are non-negotiable at the start of a relationship and typically look like:
- Per-transaction cap: £500–£2,500 per card transaction, varying by acquirer and your KYC tier.
- Daily per-cardholder limit: £1,000–£5,000 per 24-hour period per card.
- Monthly per-cardholder limit: £5,000–£15,000 per calendar month, applied at the exchange level.
These limits are set by the acquiring agreement and occasionally by card scheme rules. They can be renegotiated after 6–12 months of clean processing history, but initial limits are firm. Plan your UX and customer tier structure around them — customers who hit limits and cannot deposit are a conversion problem that acquiring terms create, not technical architecture.
Chargeback Patterns and Prevention
Crypto exchange chargebacks follow a pattern that is partly predictable and partly structural. The three dominant reason codes in practice:
Price volatility disputes
A customer purchases crypto when the price is high, the price falls, and they attempt to recover their fiat by disputing the original card transaction. Common claim: "merchandise not received" (Visa reason code 13.1) even though the crypto was delivered. This is defensible with wallet delivery logs and 3DS authentication, but it requires that evidence to have been captured contemporaneously — not reconstructed after the dispute.
Account takeover chargebacks
A legitimate customer's exchange account is compromised, crypto is purchased and moved, and the cardholder disputes transactions they genuinely didn't initiate. These are harder to defend because the fraud claim is legitimate — your KYC controls didn't prevent the account compromise. Strong second-factor authentication on card deposit flows (not just account login) materially reduces exposure here.
Family or shared-card disputes
Standard in most high-risk verticals. Defensible with 3DS and KYC but difficult when the cardholder is the account holder's household member and the KYC was completed in the account holder's name only.
3DS is not optional for crypto
Some exchanges implement 3DS only for transactions above certain thresholds to reduce friction for smaller purchases. For card acquiring stability, 3DS on every card transaction is strongly advisable regardless of amount. Your acquirer's chargeback ratio is calculated on total volume, not just large transactions — high volumes of small unauth'd transactions compound quickly.
Reserve Structures and Cash Flow Planning
Rolling reserves for crypto exchanges run higher and longer than most other high-risk categories: 10–15% withheld over 120–180 days is standard for new relationships. The extended window reflects the longer dispute lifecycle for crypto-related reason codes — some chargebacks can be filed well beyond the standard 120-day dispute window under certain card scheme rules.
For an exchange processing £1M/month with a 12% rolling reserve over 150 days, the steady-state working capital locked in reserves is approximately £600,000. This is not unusual, but it should be modelled into cash flow planning before you apply — not discovered after go-live.
What Rates to Expect
| Monthly Volume | Typical MDR | Achievable with History |
|---|---|---|
| £250k – £1M | 5.0% – 8.0% | 4.5% – 6.5% |
| £1M – £5M | 4.0% – 6.5% | 3.5% – 5.0% |
| £5M – £30M | 3.5% – 5.5% | 2.8% – 4.5% |
These rates assume FCA registration, sub-1% chargeback ratios, and at least 6 months of clean processing history. New exchanges without processing history will sit at the higher end of each range. Rates above 8% for meaningful volume should be treated as a signal to seek alternative acquirer options — the specialist market is competitive enough that pricing above that level is rarely justified by risk profile alone.