What is an Acquirer Reference Number (ARN)?

Waiting for a refund that never seems to arrive, or spotting a card transaction you don’t recognise can be frustrating—especially when you don’t know how to investigate it. These issues often stem from limited visibility into how card payments move through banking systems, making them harder to resolve without the right tools.

One such tool is the Acquirer Reference Number (ARN), a unique identifier that helps track transactions across banks. Understanding how ARN numbers work is essential for resolving disputes, tracing refunds, and confirming payments.

In this guide, we've explained what an Acquirer Reference Number (ARN) is, how it works, and the exact steps UK residents can take to find and use one to track payments and resolve disputes.

We've also explained how Wise Business can support businesses handling transactions with greater clarity using Wise Business.

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Key Takeaways

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What is an acquirer reference number (ARN)?

An Acquirer Reference Number, or ARN, is a unique code assigned to any transaction made with a credit or debit card². Think of it as a tracking number for your payment as it moves through the banking network.

When you make a purchase, the payment travels from your bank (issuer) to the merchant’s bank (acquirer). The acquirer assigns the ARN—typically around 23 digits for Visa and Mastercard—which becomes the shared reference for both banks.

Its purpose is to help track transactions. If an issue arises, such as a delayed refund, the ARN enables banks to locate and verify the payment status efficiently³.

Why you might need an ARN number in the UK

For UK residents, there are several common situations where an ARN can be useful.

Tracking a delayed refund

This is one of the most common uses of an ARN¹. If a merchant confirms a refund but it hasn’t appeared, the ARN can help your bank trace the payment.

Disputing an unrecognised transaction

If you see a transaction you don’t recognise, your bank may use the ARN to investigate and communicate with the merchant’s bank².

Following up on failed or complex payments

For international or high-value payments, an ARN helps identify where a transaction may have been delayed or interrupted³.

Providing proof of payment

An ARN can serve as confirmation that a transaction was processed by the merchant’s bank³.

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💡For businesses dealing with international transactions, Wise Business can simplify the process, as you can pay suppliers and receive payments in over 40+ currencies at the mid-market rate with low, transparent fees.

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*Disclaimer: The UK Wise Business pricing structure is changing with effect from 26/11/2025 date. Receiving money, direct debits and getting paid features are not available with the Essential Plan which you can open for free. Pay a one-time set up fee of £50 to unlock Advanced features including account details to receive payments in 22+ currencies or 8+ currencies for non-swift payments. You’ll also get access to our invoice generating tool, payment links, QuickPay QR codes and the ability to set up direct debits all within one account. Please check our website for the latest pricing information.

How to get an ARN number in the UK

You cannot locate an ARN yourself¹. Instead, you need to request it from your bank or the merchant.

1. Identify the transaction

Gather details such as date, merchant name, and amount⁶.

2. Contact your bank

Reach out using official customer support channels and explain the issue clearly.

3. Request the ARN

Ask your bank to trace the transaction and provide the ARN. In some cases, the merchant may supply it¹.

4. Wait for confirmation

It may take a few business days for your bank to retrieve the ARN.

The role of the bank and card issuer in ARN transactions

The merchant’s bank generates the ARN², while your bank acts as your main point of contact.

You typically cannot contact the acquiring bank directly. Your bank communicates across the payment network on your behalf³.

Understanding ARN number tracking and dispute resolution

An ARN provides a consistent reference across banking systems.

When you provide it to your bank, they can use it to check the transaction status within card networks like Visa or Mastercard¹.

In disputes, such as chargebacks, the ARN is used to ensure all parties are referencing the same transaction².

Clarifying ARN numbers against other references

Are you confused by similar acronyms: AMFI vs ARN?

The ARN in this guide refers to the Acquirer Reference Number.

Another ARN—the AMFI Registration Number—is unrelated and used by financial advisors in India⁴.

Manage your business transactions with greater clarity

Using a structured approach to payments can reduce the need to trace transactions manually.

Wise Business can help businesses manage international payments with transparent fees and access to multiple currencies.

With Wise Business, you can:

• 🌍 Send money to 140+ countries at the mid-market exchange rate with no hidden fees or sneaky exchange rate markups (product availability varies by region)
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• 💵 Get local account details for 8+ currencies, including USD and EUR, to let your customers pay in a currency they know and trust - convenience for them and peace of mind for you
• 💰 Hold money in 40+ currencies
• 🔁 Convert currencies anytime at the mid-market exchange rate with low, transparent fees
• ⚡ Use the batch payments tool to create and send up to 1,000 payments in a single transfer
• 👥 Run payroll and make international payments for up to 1,000 employees all over the world - including paying suppliers using local payment methods like ACH, SEPA, and Faster Payments
• 💳 Get business debit cards with 0.5% cashback for you and your team to keep track of team expenses and spend all over the world, with real-time visibility and categorisation
• 🏢 Manage cash in 55+ currencies across international offices from a single business account and move money between business accounts in seconds (exact speeds can vary depending on individual circumstances and may not be the same for all transactions)
• 🧾 Connect and sync every business transaction to your favourite accounting software, including Xero, Quickbooks, and more
• 🔐 Create your own payment approvals process to manage your team better with customised access for different team members, roles and permissions
• 📑 Create custom professional invoices and schedule invoice payments for future dates
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• 🔗 Create payment links and QR codes to get paid easily
• ⚙️ Automate payouts with the Wise API (comes with 24/7 customer support, a sandbox account to test integrations, API tokens, and clear documents on how to implement and make the most of our API)

Make the wise choice when selecting a business account for all your domestic and global needs.

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Register for Wise Business ✍️

*Disclaimer: The UK Wise Business pricing structure is changing with effect from 26/11/2025 date. Receiving money, direct debits and getting paid features are not available with the Essential Plan which you can open for free. Pay a one-time set up fee of £50 to unlock Advanced features including account details to receive payments in 22+ currencies or 8+ currencies for non-swift payments. You’ll also get access to our invoice generating tool, payment links, QuickPay QR codes and the ability to set up direct debits all within one account. Please check our website for the latest pricing information.

Sources:

1. Checkout.com – What is an ARN
2. eMerchantPay – Acquirer Reference Number explained
3. Airwallex – What is an ARN number
4. Tata Capital – AMFI Registration Number

Sources last checked on 30 March 2026