Visa VAMP Ratio: How to Calculate It Correctly and What the Numbers Mean

Visa replaced its legacy dispute monitoring programmes (VDMP and VFMP) with the Visa Acquirer Monitoring Program (VAMP) in June 2025. The threshold structure changed simultaneously — from 2.2% to 0.9% for Excessive designation — making the transition one of the most significant changes to Visa's dispute monitoring framework in years. Many merchants operating comfortably below the old threshold found themselves at risk under the new one without realising it.

Calculating your VAMP ratio correctly is a prerequisite for knowing where you stand. The formula is not what most merchants assume.

The VAMP Formula (and Why It's Different From Your Dispute Rate)

The VAMP ratio uses a specific formula that differs from the dispute rate you see in your processor dashboard in two critical ways: what's in the numerator and which month's volume is in the denominator.

The formula:

(TC40 reports + TC15 disputes) ÷ Prior month settled transactions

TC40 fraud reports are the card network's fraud reporting mechanism — filed by issuers when a transaction is identified as fraudulent, regardless of whether a formal chargeback has been filed. These are often counted separately from chargebacks in processor dashboards, which means merchants who track only their chargeback count are missing a significant portion of their VAMP numerator.

TC15 disputes are the chargeback count — what appears in your Stripe disputes dashboard, your Shopify Payments disputes section, or your acquirer's chargeback report.

Prior month settled transactions is the denominator. Not this month's transactions — last month's. A merchant who processed 10,000 transactions in May and has 95 disputes in June has a June VAMP ratio calculated against May's settlement volume, not June's. This timing difference is the most common source of discrepancy between a merchant's internal ratio calculation and their acquirer's VAMP figure.

Early Warning vs Excessive vs High Excessive Thresholds

VAMP has three monitoring tiers:

| Tier | Threshold | Status | |---|---|---| | Early Warning | 0.65% | Pre-monitoring — no fines, acquirer notified | | Excessive | 0.9% | Programme entry — acquirer fines begin | | High Excessive | 1.8% | Elevated fine schedule | | Critical | 2.0% for 3+ consecutive months | Formal remediation required |

European merchants face a stricter Early Warning threshold of 0.5%, with the Excessive threshold remaining at 0.9%. The EU threshold structure reflects Visa's different risk profile assessments by region.

Early Warning is often misunderstood as a safe zone. It is not — it is a notification that triggers increased acquirer scrutiny, and acquirers under VAMP pressure may impose their own requirements (additional reserves, operational reviews, processing restrictions) at the Early Warning tier.

Why Your Acquirer's Number May Differ From Yours

Three reasons explain most discrepancies between a merchant's self-calculated VAMP ratio and their acquirer's figure.

TC40 inclusion. If your internal calculation only counts chargebacks and not TC40 fraud reports, you are systematically understating your numerator. TC40 reports can account for 20–40% of a merchant's total VAMP numerator depending on vertical and fraud profile.

Prior-month denominator. If you divide this month's disputes by this month's transactions, your ratio will differ from Visa's calculation, which uses prior month settlement volume. During high-growth periods, this discrepancy works in your favour (denominator is lower under Visa's calculation). During volume contractions, it works against you.

Settlement vs authorisation timing. Transaction counts differ depending on whether the processor reports authorisations, settled transactions, or net settled transactions (after refunds). VAMP uses settled transactions. Merchants with significant refund volume will see their denominator reduced accordingly.

Resolving discrepancies requires getting your acquirer's raw VAMP reporting, not the processed version in most dispute dashboards, and reconciling numerator and denominator inputs directly.

ChargeMate maintains a free VAMP calculator at chargemate.tech/vamp-calculator that applies the correct formula — including the prior-month transaction denominator that most internal spreadsheets get wrong.

Early Warning vs Excessive vs High Excessive Thresholds in Practice

An Excessive designation occurs in the month when the ratio first crosses 0.9% — there is no grace period. Acquirers receive Visa's monthly VAMP report and are required to take action, which typically means a formal notification letter to the merchant and the start of a remediation discussion.

High Excessive at 1.8% triggers a higher fine schedule and often more aggressive acquirer intervention. Critical designation at 2.0% for three consecutive months has resulted in processor termination in documented cases, with merchant accounts placed on Mastercard's MATCH list.

How to Track Your VAMP Ratio Weekly

Monthly tracking is insufficient. By the time a monthly VAMP report shows a problem, you have already spent an entire month accruing exposure. Weekly tracking requires pulling two figures weekly:

1. Cumulative TC40 + TC15 count for the month-to-date
2. Prior month's total settled transaction count (fixed for the month)

Divide the cumulative dispute figure by the prior month denominator. If week three of the month already shows a 0.7% ratio, you have a strong signal the month will breach Excessive without intervention.

Setting internal alert thresholds at 0.5% (act before Early Warning) and 0.75% (act before Excessive) gives you response time that monthly monitoring does not. The chargeback alert services available through acquirers — Verifi for Visa disputes — are particularly valuable for merchants near these thresholds, because they stop disputes before they enter the TC15 count entirely.