> ## Documentation Index > Fetch the complete documentation index at: https://docs.pay.aptahq.com/llms.txt > Use this file to discover all available pages before exploring further. # Charge — money in > **Charge a customer — the money-in entry point.** This is what your app calls when a user taps "Pay": you hand over an amount, a country, a method and the payer's identifier, and the gateway asks the routed provider to debit them. Typical use is a checkout or top-up flow — a race entry fee, a wallet load, an order payment. ONE call. The customer-facing prompt (momo PIN, redirect page, OTP) is the provider's own; the gateway hands you back a canonical status you branch on instead of a provider-shaped payload. A charge does not settle synchronously — expect `pending` and treat the webhook (or a poll of `GET /v1/collections/{reference}`) as the real answer. Returns 201 with a gateway `reference` — persist it. It is your handle for polling, for the webhook you will receive, and for a later refund. **`Idempotency-Key` is required**; this moves money. Replaying a completed key returns the original response verbatim with no second charge, so a retry after a network timeout is always safe. **Ghana (GHS) requires `redirect_url`** and answers `requires_action` with a `next_action.redirect_url` — send the user there to finish. **No OTP is required.** A momo charge goes to the provider on this one call and the customer approves it on their handset prompt alone — Kenya, Rwanda, Uganda and Ghana alike. Nothing to collect, nothing to post back. The `otp` field remains accepted, and so does the ladder behind it, for the case where a corridor is configured to demand a code: there a charge sent without an `otp` texts the customer one, records the transaction, and answers `201` with `status: "requires_action"` and a `next_action` of type `otp` carrying the `pin_id` — collect the code and post it to `POST /v1/collections/{reference}/authorize`, which validates it AND charges. **Always branch on `next_action` rather than assuming its absence**, so your integration is unaffected either way and keeps working on a provider that does require one. **Amounts are integer minor units, and UGX/RWF/XAF/XOF are zero-decimal**: 2000 UGX is `2000`, not `200000`. Getting this wrong is a 100x error. **Double-charge guard.** Before charging, the gateway checks whether a momo charge to this same number is already live for your tenant (last 15 minutes). If one is, it asks the provider what actually happened: - The earlier charge **succeeded** (its webhook was lost) — this request is refused `409 duplicate_charge_in_flight` with `already_succeeded: "true"` and the earlier `reference`. Show that as a receipt; do not retry. - The earlier charge **failed or expired** — it is settled and THIS charge proceeds normally. - The earlier charge is **still live**, or the provider cannot be reached — refused `409 duplicate_charge_in_flight`. Wait and poll `GET /v1/collections/{reference}`. This is separate from `Idempotency-Key`, which protects a retried API call. This protects a retried CUSTOMER action, which arrives with a brand-new key. ## OpenAPI ````yaml /openapi.json post /v1/collections openapi: 3.0.3 info: title: AptaPay Gateway version: 1.0.0 description: > One provider-neutral payment API owned by many apps: collections, payouts, bank resolution and FX, with signed webhooks back. ## Authentication Every `/v1/*` request carries four headers. **A plain API key is not enough** — a key in a proxy log or an error report would be immediately usable, whereas a signature binds the request to a body and a moment. | Header | Value | | --- | --- | | `X-AptaPay-Key` | `{app_id}.{key_id}.{api_key}` | | `X-AptaPay-Timestamp` | unix seconds | | `X-AptaPay-Nonce` | 16-64 chars, `[A-Za-z0-9_-]`, unique per request | | `X-AptaPay-Signature` | `v1={hex HMAC-SHA256}` | The signature is HMAC-SHA256, with your **inbound** signing secret, over exactly these ten fields joined by `\n`: ``` v1 {APP_ID} {KEY_ID} {HOST} lowercased {METHOD} uppercased {PATH} no query, NOT url-decoded {CANONICAL_QUERY} sorted, RFC3986-encoded, "" when absent {TIMESTAMP} {NONCE} {SHA256_HEX(RAW_BODY)} sha256("") for GET/DELETE ``` Every field earns its place. `CANONICAL_QUERY` is in there because without it `?limit=1` and `?limit=100000` sign identically, so a captured read signature could be replayed to dump everything. `HOST` stops a signature captured against one deployment replaying into another. The timestamp window is **asymmetric**: `-120s <= now - ts <= +30s`. A symmetric window is a ten-minute replay window, and there is no legitimate reason to sign in the future beyond small clock skew. A working reference implementation is in `docs/TENANT_INTEGRATION.md`, and `scripts/sign_request.mjs` signs a request from the terminal. ## Idempotency `Idempotency-Key` is **required** on every money-moving POST. A missing key is a 400 — the server never invents one, because a server-generated key is unique per request and protects nothing, which is worse than none because it looks like protection. - Replaying a completed key returns the **original response verbatim**, with its original status code. No second provider call. - The same key with **different parameters** is a 422, never a replay. - A concurrent duplicate is a 409 `request_in_progress`. ## Errors Branch on `error.code` and the three booleans, never on the HTTP status: `terminal` (reverse and tell the user), `retriable` (retry with the same key), `ambiguous` (**do not reverse** — poll instead). ## Amounts Integer minor units, with a per-currency exponent. **UGX, RWF, XAF and XOF are zero-decimal**: 2000 UGX is `2000`. Getting this wrong is a 100x error. ## Test mode is NOT a sandbox **Every request reaches a real provider. There is no sandbox, and no test host.** AptaPay routes to a single upstream provider, and that provider publishes exactly one API host for live and test traffic alike. No sandbox base URL exists anywhere in its reference documentation. So "test mode" here does not mean what it means on Stripe. It is a **second, real provider account** holding a small real balance, reached over the same wire as production. A test-mode payout moves real money out of a real wallet to a real phone number. It cannot be reversed, because the provider exposes no refund endpoint. | | What you might expect | What actually happens | | --- | --- | --- | | Host | a separate sandbox host | the one production host, always | | Money | simulated | real, in a real wallet | | Recipients | fake numbers accepted | real MSISDNs, really credited | | Undo | reverse the test charge | none — no refund endpoint exists | Two guardrails stand in for the sandbox, and they are permanent, not temporary scaffolding: - **A hard amount ceiling on every test-mode transaction**, enforced by this gateway *before* any provider call. Over it, you get a `422` and no request ever leaves. - **`is_test_mode` stamped on every transaction record**, so a test transaction is identifiable forever after the fact. Mode is a property of **which credentials you hold**, never of a request field — there is no `test: true` to send, and no header that switches it. A live key transacts live; that is the only thing that decides it. See `GET /healthz` for which mode a deployment is running. ## CORS There isn't any, deliberately. This is a server-to-server API and browsers must never call it: signing from client-side JS would put your secret in view-source. Cross-origin browser requests are denied. servers: - url: https://api.pay.aptahq.com description: >- Production. There is no sandbox host, because the upstream provider has none — see "Test mode is NOT a sandbox". Sign the host you dial: the host is part of the canonical string, so a request dialled here must claim `api.pay.aptahq.com`. security: - AptaPaySignature: [] tags: - name: Collections description: Money in. - name: Payouts description: Money out. - name: Refunds description: Reversals — 501 where the routed provider has no refund endpoint. - name: Transactions description: The gateway's own ledger of what it was asked to do. - name: Beneficiaries description: Saved recipients. Stored masked, names re-resolved at payout time. - name: Reference description: Corridors, banks, countries, balances, capability matrix. - name: Float description: Your own claim on the shared wallet pool — what you can actually pay out. - name: FX description: Exchange between your own wallets. Quote is free; exchange moves money. - name: Webhooks description: Provider ingress. Documented for completeness; tenants never call it. - name: Ops description: Health. paths: /v1/collections: post: tags: - Collections summary: Charge — money in description: > **Charge a customer — the money-in entry point.** This is what your app calls when a user taps "Pay": you hand over an amount, a country, a method and the payer's identifier, and the gateway asks the routed provider to debit them. Typical use is a checkout or top-up flow — a race entry fee, a wallet load, an order payment. ONE call. The customer-facing prompt (momo PIN, redirect page, OTP) is the provider's own; the gateway hands you back a canonical status you branch on instead of a provider-shaped payload. A charge does not settle synchronously — expect `pending` and treat the webhook (or a poll of `GET /v1/collections/{reference}`) as the real answer. Returns 201 with a gateway `reference` — persist it. It is your handle for polling, for the webhook you will receive, and for a later refund. **`Idempotency-Key` is required**; this moves money. Replaying a completed key returns the original response verbatim with no second charge, so a retry after a network timeout is always safe. **Ghana (GHS) requires `redirect_url`** and answers `requires_action` with a `next_action.redirect_url` — send the user there to finish. **No OTP is required.** A momo charge goes to the provider on this one call and the customer approves it on their handset prompt alone — Kenya, Rwanda, Uganda and Ghana alike. Nothing to collect, nothing to post back. The `otp` field remains accepted, and so does the ladder behind it, for the case where a corridor is configured to demand a code: there a charge sent without an `otp` texts the customer one, records the transaction, and answers `201` with `status: "requires_action"` and a `next_action` of type `otp` carrying the `pin_id` — collect the code and post it to `POST /v1/collections/{reference}/authorize`, which validates it AND charges. **Always branch on `next_action` rather than assuming its absence**, so your integration is unaffected either way and keeps working on a provider that does require one. **Amounts are integer minor units, and UGX/RWF/XAF/XOF are zero-decimal**: 2000 UGX is `2000`, not `200000`. Getting this wrong is a 100x error. **Double-charge guard.** Before charging, the gateway checks whether a momo charge to this same number is already live for your tenant (last 15 minutes). If one is, it asks the provider what actually happened: - The earlier charge **succeeded** (its webhook was lost) — this request is refused `409 duplicate_charge_in_flight` with `already_succeeded: "true"` and the earlier `reference`. Show that as a receipt; do not retry. - The earlier charge **failed or expired** — it is settled and THIS charge proceeds normally. - The earlier charge is **still live**, or the provider cannot be reached — refused `409 duplicate_charge_in_flight`. Wait and poll `GET /v1/collections/{reference}`. This is separate from `Idempotency-Key`, which protects a retried API call. This protects a retried CUSTOMER action, which arrives with a brand-new key. operationId: createCollection parameters: - $ref: '#/components/parameters/IdempotencyKey' requestBody: required: true content: application/json: schema: type: object required: - amount_minor - currency - country - method - source properties: amount_minor: $ref: '#/components/schemas/MinorUnits' currency: $ref: '#/components/schemas/Currency' country: type: string example: UG method: type: string enum: - momo - bank - card source: $ref: '#/components/schemas/CollectionSource' redirect_url: type: string description: REQUIRED for GHS collections. narration: type: string metadata: type: object description: >- Free-form correlation data, stored on the transaction and ECHOED BACK on every webhook delivery as `data.metadata`. This is how you map an AptaPay reference to one of your own: our `reference` is opaque and carries no structure you can parse, so put your order id or reference here at charge time and read it back off the callback. Must serialize to at most 4096 bytes — it is re-sent on every delivery attempt. customer: type: object description: >- Optional payer details for the PROVIDER's records and receipts. Never used for routing or matching, and not persisted on the transaction — it is passed straight through, so send only what you are willing to share with the provider. properties: name: type: string email: type: string otp: type: object description: >- **Optional — this account is whitelisted for phone verification, so no corridor requires an OTP.** Supply it only if you already drove `POST /v1/collections/otp` yourself: `pin_id` from that call, `pin` from what the customer typed. On a corridor configured to require a code, omitting this starts the OTP ladder rather than failing. required: - pin_id - pin properties: pin_id: type: string pin: type: string examples: ugandaMomo: summary: >- START HERE — no otp needed. Goes straight to the provider; the customer approves on their handset value: amount_minor: 2000 currency: UGX country: UG method: momo source: type: momo msisdn: '0781234567' network: MTN country: UG narration: Race entry ugandaMomoWithOtp: summary: >- Optional — already drove /collections/otp yourself? Supply the code here (set otp_pin_id and otp_pin first) value: amount_minor: 2000 currency: UGX country: UG method: momo source: type: momo msisdn: '+256781234567' network: MTN country: UG otp: pin_id: '{{otp_pin_id}}' pin: '{{otp_pin}}' narration: Race entry ghanaRedirect: summary: Ghana — redirect_url is mandatory value: amount_minor: 1050 currency: GHS country: GH method: momo redirect_url: https://laces.example/return source: type: momo msisdn: '+233201234567' country: GH responses: '201': description: >- Accepted. Normally the charge is already with the provider — no OTP is required on any corridor. `status` is `requires_action` only where a corridor still demands a code or a redirect; branch on `next_action.type` and finish at `/authorize`. content: application/json: schema: $ref: '#/components/schemas/APIResult' examples: requiresOtp: summary: OTP ladder started — a code was texted to the customer value: code: 201 message: OK data: reference: APT-LCS-V1StGXR8Z5jdHi6BmyT provider: eversend status: requires_action observed_amount_minor: 2000 observed_currency: UGX next_action: type: otp pin_id: a435fdbc-a0b3-4412-848c-2dbc0956e5c6 message: >- Enter the code sent to the number ending 4235, then POST it to /v1/collections/APT-LCS-V1StGXR8Z5jdHi6BmyT/authorize. acceptedDirectly: summary: The normal case — already with the provider, no OTP value: code: 201 message: OK data: reference: APT-LCS-V1StGXR8Z5jdHi6BmyT provider: eversend status: pending observed_amount_minor: 2000 observed_currency: UGX '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/Unauthorized' '403': description: > `tenant_frozen` (your tenant has been frozen and cannot move money — contact support) or `destination_blocked` (the payer has been blocked). No provider call was made in either case. content: application/json: schema: $ref: '#/components/schemas/APIResult' '409': $ref: '#/components/responses/Conflict' '422': $ref: '#/components/responses/Unprocessable' components: parameters: IdempotencyKey: name: Idempotency-Key in: header required: true schema: type: string maxLength: 255 description: | Required. A missing key is a 400 — never a server-generated one. example: laces-order-8f14e45f schemas: MinorUnits: type: integer description: > An integer count of the currency's smallest unit. NEVER a float, and never a decimal major amount. The `_minor` suffix on a field name is part of the contract: `amount` could be read as `20.00` or `2000`, whereas `amount_minor` can only be read one way. **The exponent is PER CURRENCY.** There is no universal "cents": | Exponent | Currencies | `2000` means | |---|---|---| | **0** (zero-decimal) | UGX, RWF, XAF, XOF | 2,000 shillings/francs | | **2** | KES, GHS, NGN, TZS, ZMW, USD, EUR, GBP | 20.00 | So `2000` UGX is two thousand shillings, while `2000` KES is twenty. Applying a blanket x100 to a zero-decimal currency is a **100x money error** — the kind that reconciles to nothing months later. To send an amount, multiply the major amount by `10^exponent` and confirm the result is an exact integer (KES `19.99` -> `1999`). To display one, divide by `10^exponent` for presentation only — keep the minor-unit integer as the value you store, compare, and sum. Rules the gateway enforces: - **An unknown currency is rejected, never defaulted.** A currency with no declared exponent fails with `unknown_currency` rather than assuming 2, because a silent wrong exponent is worse than a loud failure. - **A non-exact amount is rejected, never rounded.** KES `19.999` fails with `inexact_amount`. AptaPay will not decide on your behalf which way to round someone's money. - **Amounts are never floats internally.** Providers send amounts as strings (`"2000"`) AND sometimes as numbers, so parsing is deliberate at the adapter boundary and converts to an exact integer or fails. A field's exponent always follows the currency named alongside it. On an FX quote, `source_amount_minor` and `destination_amount_minor` routinely use DIFFERENT exponents in the same response. example: 2000 Currency: type: string enum: - UGX - RWF - XAF - XOF - KES - GHS - NGN - TZS - ZMW - USD - EUR - GBP CollectionSource: oneOf: - $ref: '#/components/schemas/CollectionMomoSource' - $ref: '#/components/schemas/BankDestination' discriminator: propertyName: type APIResult: type: object description: > The single response envelope, used by EVERY endpoint so a consuming app parses one shape everywhere. required: - code - message properties: code: type: integer example: 200 message: type: string example: OK data: description: Present on success. Shape varies per endpoint. error: $ref: '#/components/schemas/GatewayErrorBody' CollectionMomoSource: type: object description: > A momo source on a COLLECTION. `country` is optional here and defaults to the request's top-level `country`. Collections pull money: a wrong corridor fails or produces a refundable charge, so inheriting is safe. The payout side is deliberately stricter — see `PayoutMomoDestination`. required: - type - msisdn properties: type: type: string enum: - momo msisdn: type: string description: > The customer's phone number in whatever form they typed it. All of `0772123456`, `256772123456`, `+256772123456` and the bare national `772123456` are accepted, with spaces, dashes and parentheses ignored. The platform normalises to E.164 WITH the leading `+` (`+256772123456`) using the country code of the resolved corridor — so a missing country code is supplied, never guessed from the digits. The number is validated AGAINST the corridor: one carrying a different country's calling code, or the wrong national length, is rejected with `invalid_msisdn` rather than reinterpreted. example: '0772123456' network: type: string description: > Network code, a free string from the corridor table — never a closed enum, so a network can be added in Firestore with no schema change. example: MTN country: type: string description: > Optional. Defaults to the request's top-level `country`. Supply it only to state the number's country explicitly; when present it is still validated against the number, so a mismatch is an error. example: UG BankDestination: type: object required: - type - country - bank_code - account_number properties: type: type: string enum: - bank country: type: string example: NG bank_code: type: string example: '044' bank_name: type: string account_number: type: string example: '0011223344' account_name: type: string description: > Advisory only. The gateway RE-RESOLVES the account name at payout time, every time — a stale "yes, this is Jane Doe" can outlive the account being closed, renamed, or reassigned. msisdn: type: string example: '+256763494235' description: > The RECIPIENT's phone number. Not needed to reach the account, but the upstream provider REQUIRES a contact number on bank payouts and rejects an empty one — so a bank payout routed upstream without this is refused as `validation_failed` naming `destination.msisdn`. Accepted in local format (`0763494235`) and normalised to E.164 against `destination.country`. GatewayErrorBody: type: object description: > Machine-readable error classification. EXACTLY ONE of terminal/retriable/ ambiguous is true. laces_api inferred this from the HTTP status and got it wrong, stranding real money twice (2026-08-15, 2026-08-16). Branch on these booleans, never on the status code: terminal -> the provider refused. Reverse the debit and tell the user. retriable -> safe to retry with the SAME Idempotency-Key. ambiguous -> the outcome is UNKNOWN. Do NOT reverse. Poll instead. required: - code - message - terminal - retriable - ambiguous properties: code: type: string description: Stable machine code. Branch on this, never on `message`. example: payout_rejected_by_provider message: type: string description: > Human text from a compiled-in map. NEVER provider text — a stringified provider error can carry an Authorization header. terminal: type: boolean retriable: type: boolean ambiguous: type: boolean details: type: object additionalProperties: type: string responses: BadRequest: description: Validation failed. content: application/json: schema: $ref: '#/components/schemas/APIResult' Unauthorized: description: > Missing, malformed, stale, replayed or invalid signature. Also returned when a body was sent but its raw bytes were unavailable — verified-as-empty must never mean processed-as-full. content: application/json: schema: $ref: '#/components/schemas/APIResult' Conflict: description: '`request_in_progress`, `quote_expired`, or `indeterminate_outcome`.' content: application/json: schema: $ref: '#/components/schemas/APIResult' Unprocessable: description: > Semantically refused BEFORE any provider call — corridor unsupported, amount caps, insufficient float, or an idempotency key reused with different parameters. content: application/json: schema: $ref: '#/components/schemas/APIResult' securitySchemes: AptaPaySignature: type: apiKey in: header name: X-AptaPay-Signature description: > `v1={hex HMAC-SHA256}` over the ten-field canonical string. Sent alongside `X-AptaPay-Key`, `X-AptaPay-Timestamp` and `X-AptaPay-Nonce` — all four are required. OpenAPI can only model one header per scheme, so the other three are described in the Authentication section above. ````