Understanding Mastercard Chargeback Reason Code 4831: Transaction Amount Differs

Reason Code 4831 occurs when a cardholder sees a different transaction amount on their statement from what they expected. There are numerous root causes, but the outcome is the same: they feel they have been incorrectly charged and raise a dispute. Although this code is now merged into 4834, issuers may still use 4831 on some disputes.

Key Takeaways

• What it means: The processed amount was different from the total the cardholder agreed to.
• Causes: Missing disclosure. Forgotten price adjustments. Currency conversion. Input errors.
• How to respond: Send proof of the cardholder’s authorisation. Or, supply evidence of a prior refund.
• How to prevent: Display all fees. Gain new authorisation for any change. Use chargeback alerts for early warning.

What is a Mastercard Reason Code 4831 Chargeback?

Note: Reason Code 4831 has now been discontinued and is included under Reason Code 4834. However, the advice below is still relevant to Reason Code 4834 chargebacks relating to "Transaction Amount Differs".

A Reason Code 4831 chargeback arises when the final transaction value on a cardholder’s statement does not match the amount they accepted at checkout or at the point-of-sale. In Mastercard terminology, the dispute falls under a “Point-of-Interaction Error”. A simple example is a hotel guest who books a room for £120 online but later sees a £150 charge because a non-refundable resort fee was added. If the guest did not clearly see or approve that fee, they may ask their bank to reverse the whole payment. 

The bank then files a 4831 chargeback with the acquirer, withdrawing the funds from the merchant account until the matter is resolved. Because the underlying question is straightforward: “Did the cardholder give informed consent?”, merchants who keep clear records often win their representment.

Primary Causes for a Code 4831 Chargeback

Most 4831 disputes stem from communication gaps. A common cause is undisclosed extras. Online retailers may add insurance, resort, or handling fees after the customer has clicked “Pay”. In-store staff may key in a gratuity or service charge without first showing the new total to the customer.

Currency conversions can be to blame. Let's say you use dynamic currency conversion, and the rate changes between the authorisation and settlement. That will mean the customer sees a different amount on their statement than they remember approving. Even a slight difference can prompt them to raise a dispute.

One of the most common causes can be simple human error, especially when using manual entry of amounts. A waiter may key £71.50 instead of £17.50; a clerk may mix up a decimal point. Even when corrected later, the original overcharge might still prompt the cardholder to contact the issuer.

Finally, friendly or intentional fraud cannot be ignored. Some shoppers claim ignorance of a legitimate surcharge in the hope of a refund. They may allege that the variable amount exceeded what they “remember” consenting to, shifting the burden of proof to the merchant.

Time Limit for Disputing a Mastercard Reason Code 4831 Chargeback

Issuers must submit a 4831 dispute within 90 calendar days of the processing date. Once the acquirer receives the chargeback, the clock shifts to the merchant. You have 45 calendar days to answer. Missing that time limit forfeits the right to challenge, and the chargeback stands permanently.

During those 45 days, you must gather the documents, draft the rebuttal letter, and send everything to the acquirer. They then forward your second presentment to the issuer. Mastercard may ask for extra information, so sending complete evidence the first time is wise.

If you refund the customer before receiving the chargeback, supply dated proof of the refund. A dated credit memo will help you dismiss the dispute quickly. If you need more than 45 days (for example, if you are waiting for a guest to return paperwork), contact your processor at once to see if they will extend the deadline; however, this is unlikely, so you shouldn't count on it as a solution.

What 4831 Means for Consumers & Issuers

For consumers, code 4831 is a safeguard against hidden fees and keying errors. It reassures them that the price displayed is the price they will pay. When they notice a mismatch, they can ask their bank to investigate rather than negotiate with the merchant.

Issuers view 4831 as a service standard. Quick dispute resolution keeps cardholders loyal and reduces call-centre traffic. The bank’s first task is to confirm the cardholder’s claim. They review statements, receipts, and any merchant correspondence supplied by the cardholder. If the documentation suggests the amount was wrong or unclear, the issuer files the chargeback.

Issuers must also weigh regulatory liabilities. Under the Payment Services Regulations, UK banks are obliged to return unauthorised payments promptly. Misstated amounts can fall into that category. Therefore, issuers err on the side of the cardholder when evidence is inconclusive. Clear merchant records help the bank rule out true unauthorised activity, benefiting all parties.

What 4831 Means for Merchants

Although relatively simple to win, 4831 disputes still drain resources. Each case can lead to a chargeback fee, plus the temporary loss of the transaction value. Repeated disputes raise the chargeback-to-sales ratio, risking higher processing costs or even losing the merchant account.

A further impact is reputational. Customers who feel overcharged often complain publicly. In sectors such as hospitality, negative reviews can outweigh the value of a single sale. Operationally, the code highlights weaknesses in the billing workflow. Frequent 4831s suggest unclear pricing or training gaps at the till. Fixing those weaknesses usually lowers other dispute categories too, boosting net income.

Finally, merchants should note that Mastercard’s migration to code 4834 does not remove liability. If your contracts, receipts, or POS prompts do not show the full cost, the revised code will still pull back funds. Treat every 4831 as a signal to tighten controls, refine communication, and protect revenue.

How to Respond to a Code 4831 Chargeback

Begin by reading the dispute message carefully. Check the amount in question and the transaction date. Locate the original order, receipt, or booking confirmation. Confirm whether the total shown there matches what you charged.

If the cardholder saw and accepted the final amount, compile the evidence. For e-commerce, provide the checkout page that displays the figure, the terms of service, and any tick-box or digital signature proving consent. For card-present sales, include the signed receipt or the PIN-verified authorisation log. Highlight the matching totals.

Where you quoted a range--common in fuel dispensing or car hire--attach the written notice of the upper limit and show that the captured sum sits within it.

If you have already credited the difference, send the refund receipt with the bank reference, demonstrating that the cardholder is not out of pocket.

Write a concise rebuttal letter stating that the cardholder authorised X and was charged Y, or provide the date the overcharge was corrected. Use plain language and avoid unnecessary detail. Make sure that you or your team submits the package to your acquirer in good time, staying well inside the 45-day window.

If you discover that the customer was not informed, accept the chargeback swiftly and apologise to the cardholder, then take time to review internal procedures to stop a repeat.

Proactive Prevention: The Ultimate Defence

Transparent billing is the simplest defence. Display all taxes, fees, and optional extras before the customer commits. If a change is needed later (damaged equipment, late checkout), obtain new consent in writing or through an authenticated digital prompt. Train staff to void and re-run a sale if the payment method changes mid-transaction.

Technology helps. Real-time monitoring flags mismatched totals, and audit trails make representment easier. Chargeback alert services give you early notice of a pending dispute. This gives you time to refund or clarify matters before the issuer finalises a chargeback. To see how this works in practice, try out Chargeback.io.