Concepts and glossary
Definitions for the terms used throughout these docs. Each term has a deep-link anchor. For example, DMS jumps to the DMS definition. Larger concepts get a short summary here with a link to the full feature page.
Jump to: A · C · D · F · H · M · P · R · S · T · V
Letters that have no entries are omitted from the index.
A
ACS
Access control server. The issuer's server that hosts 3-D Secure authentication. During a 3DS challenge, the Checkout page redirects the customer to the ACS to authenticate with their bank; the ACS then redirects back to your site.
APM
Alternative payment method. A non-card payment method, such as PayPal, iDEAL, Sofort, bank transfers, wallets, and crypto on/off-ramps. See the S2S APM guide.
ARN
Acquirer reference number. Identifies a transaction in card-network reconciliation. Useful when investigating chargebacks with your acquirer.
C
Capture
The second stage of a DMS payment. Transfers funds that were previously held by an authorization, performed via /api/v1/payment/capture, scheduled auto-capture, or admin panel. After capture, refund is the only way to return funds.
Cascading
Automatic retry of a payment across multiple MIDs or connectors when the first attempt is declined. Configured per merchant in admin panel → Custom routing.
See also: MID, Pre-routing
Channel ID
A logical identifier that routes a payment to a specific MID. Set on the auth request via channel_id. Surfaces in callbacks for traceability.
CIT
Customer-initiated transaction. A payment the customer triggered themselves (one-off checkout, manual top-up). Contrast with MIT. 3DS and SCA rules differ by initiation type.
D
DMS
Dual-message system. A two-stage payment flow:
- Authorization holds funds on the customer's card. Triggered by
/api/v1/sessionagainst a DMS-enabled MID. - Capture transfers the held funds. Triggered by
/api/v1/payment/capture, scheduled auto-capture, or admin panel.
Used when capture should happen after a separate event, such as order shipment, marketplace settlement, or fulfilment confirmation. The authorization hold expires (typically 7 days; varies by issuer) if not captured. See DMS mode for the full flow.
DPAN
Digital primary account number. The card number a wallet (Apple Pay, Google Pay) presents at checkout. Distinct from the underlying FPAN, which stays at the issuer.
F
FPAN
Funding primary account number. The real card number behind a DPAN. Held at the issuer; never visible to the merchant.
H
HPP
Hosted payment page. A payment page rendered by the platform on its own domain; the merchant redirects the customer to it. The Checkout integration is HPP-style.
M
MID
Merchant identifier. Your account at a specific connector or acquirer. One merchant can have many MIDs (one per connector). Routing rules, DMS mode, and many other settings are configured per MID.
See also: Cascading, Pre-routing, Channel ID
MIT
Merchant-initiated transaction. A payment the merchant triggers, such as recurring charges, subscription billing, or account top-ups. Contrast with CIT. Required for recurring flows.
P
PAN
Primary account number. The card number printed on the front of the card. Subject to PCI-DSS handling rules; never stored unencrypted.
Pre-routing
Filtering of the payment methods shown on the Checkout page based on merchant rules: region, currency, BIN, and so on. Configured in admin panel → Custom routing. Bypassed when methods is explicitly set in the auth request. See Pre-routing for setup details.
Protocol mapping
The internal mapping between a merchant and a payment protocol (Checkout, S2S APM, S2S CARD, HPF). Set up during merchant onboarding by the platform team.
R
Recurring
A payment triggered by the merchant using a previously stored card token. Differs from a one-off charge in its 3DS challenge behaviour and its MIT treatment. See Recurring.
See also: MIT, Tokenization
RRN
Retrieval reference number. The acquirer's transaction identifier. Used in reconciliation, chargeback investigations, and acquirer support tickets.
S
SMS
Single-message system. A one-stage payment: authorization and capture happen together. The default mode for most MIDs. Contrast with DMS.
T
Tokenization
Storing a card so future charges can be made without the customer entering card details again. Send req_token: true in the auth request to receive a card_token in the callback; reuse it via card_token: ["..."] on later requests. Often paired with Recurring. See Tokenization.
V
Void
Cancelling a DMS authorization before capture, releasing the held funds back to the card. Triggered by /api/v1/payment/void. After capture, use refund instead.