> ## Documentation Index > Fetch the complete documentation index at: https://developers.perkstar.co.uk/llms.txt > Use this file to discover all available pages before exploring further. # Reverse a previously-posted transaction > Creates a compensating Transaction row whose `delta` is the negation of the original's, linked via `reverses_transaction_id`. Fires `TRANSACTION_CREATED` so partner webhooks notice the reversal end-to-end. Idempotent: reversing the same transaction twice returns the existing reversal at HTTP 200 (enforced by the unique constraint on `Transaction.reversesTransactionId` + a P2002 fallback). Cannot reverse: • An already-reversed transaction's reversal (post a new accrue instead). • A transaction in the opposite mode — live keys can't reverse test rows and vice versa. Pass either `transaction_id` (Perkstar's id) OR `external_transaction_id` (your POS-side id). Both forms resolve to the same underlying row. ## OpenAPI ````yaml /api/openapi.yaml post /marketplace/reverse openapi: 3.1.0 info: title: Perkstar Public REST API version: 2026-05-04.oauth description: | Programmatic access to your Perkstar loyalty data. Two authentication modes are supported: - **API key.** Per-org bearer token issued from Settings → API keys (`pk_live_…` / `pk_test_…`). Right choice for direct integrations, single-tenant POS adapters, and back-office sync. - **OAuth 2.0.** Three-legged authorization-code flow with PKCE, for marketplace listings (Square App Marketplace, Shopify App Store, Toast Partner Marketplace, Lightspeed). The merchant installs your app from the partner marketplace, lands on `/oauth/authorize`, approves the requested scopes, and your server exchanges the code at `/api/oauth/token` for a short-lived access token. See the dedicated OAuth section below. Every endpoint is scoped, rate-limited, and idempotent on POST. POS-adapter builders should start with the `/marketplace/*` endpoints — they collapse the typical "find-or-create customer + enrolment + post transaction" flow into a single round-trip with permanent dedupe via `external_transaction_id`. ## Test credentials Test credentials (`pk_test_…` or OAuth applications in TEST mode) can read API data, create isolated test transactions, and simulate wallet pushes. They cannot create, update, or delete live customers, enrolments, or webhook configuration. Test calls to `/marketplace/accrue` only work with an existing customer and enrolment; `/marketplace/enroll` is live-only. This prevents a sandbox integration from changing live customer records. Copy-paste cURL recipes are published at `/api/v1/curl-recipes.md` for teams that want to test the API before wiring the SDK. ## Response headers (universal) Every response, success or error, carries: - **X-Request-Id** — unique per request. Echo this in support tickets; we can find the exact call in the per-key audit log. - **X-API-Version** — date-versioned schema marker (`2026-05-04` as of writing). 12-month deprecation policy. - **X-RateLimit-Limit** — per-minute quota for the credential. - **X-RateLimit-Remaining** — tokens left in the current window. - **X-RateLimit-Reset** — unix-seconds when the window refills. - **Retry-After** — emitted on 429 only; seconds to wait. The reusable error responses below (`Unauthorized`, `Forbidden`, `NotFound`, `RateLimited`, `ValidationError`) declare these as strongly-typed `headers` so codegen against an error path has them. Success responses inline their `"200"` / `"201"` and rely on this convention rather than per-endpoint header declarations. contact: name: Perkstar url: https://perkstar.co.uk servers: - url: https://dashboard.perkstar.co.uk/api/v1 description: Production security: - bearerAuth: [] paths: /marketplace/reverse: post: tags: - Marketplace summary: Reverse a previously-posted transaction description: | Creates a compensating Transaction row whose `delta` is the negation of the original's, linked via `reverses_transaction_id`. Fires `TRANSACTION_CREATED` so partner webhooks notice the reversal end-to-end. Idempotent: reversing the same transaction twice returns the existing reversal at HTTP 200 (enforced by the unique constraint on `Transaction.reversesTransactionId` + a P2002 fallback). Cannot reverse: • An already-reversed transaction's reversal (post a new accrue instead). • A transaction in the opposite mode — live keys can't reverse test rows and vice versa. Pass either `transaction_id` (Perkstar's id) OR `external_transaction_id` (your POS-side id). Both forms resolve to the same underlying row. operationId: marketplaceReverse parameters: - $ref: '#/components/parameters/IdempotencyKey' requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/MarketplaceReverseRequest' responses: '200': description: Existing reversal returned (idempotent replay) content: application/json: schema: $ref: '#/components/schemas/MarketplaceReverseResponse' '201': description: Created content: application/json: schema: $ref: '#/components/schemas/MarketplaceReverseResponse' '400': $ref: '#/components/responses/ValidationError' '401': $ref: '#/components/responses/Unauthorized' '403': $ref: '#/components/responses/Forbidden' '404': $ref: '#/components/responses/NotFound' '422': $ref: '#/components/responses/ValidationError' '429': $ref: '#/components/responses/RateLimited' security: - bearerAuth: [] components: parameters: IdempotencyKey: in: header name: Idempotency-Key schema: type: string maxLength: 255 description: | Replay-safe request key. Repeated requests with the same value within 24h return the original response unchanged. schemas: MarketplaceReverseRequest: type: object description: | Exactly one of `transaction_id` or `external_transaction_id` must be supplied. properties: transaction_id: type: string external_transaction_id: type: string reason: type: string maxLength: 280 MarketplaceReverseResponse: type: object properties: transaction: $ref: '#/components/schemas/Transaction' reverses_transaction_id: type: string enrollment: type: object properties: id: type: string balance: type: number multipleOf: 0.01 redemptions_count: type: integer idempotent_replay: type: boolean description: | Set to true when the response is a replay of an existing reversal. Absent on fresh creates. Transaction: type: object properties: id: type: string enrollment_id: type: string type: type: string enum: - STAMP - REDEEM - ADJUST source: type: string enum: - SCANNER - POS - API - ADJUST - DASHBOARD - LEGACY_IMPORT - TAP delta: type: number multipleOf: 0.01 amount_pence: type: integer nullable: true note: type: string nullable: true external_id: type: string nullable: true external_transaction_id: type: string nullable: true description: | Partner-supplied stable identifier (Toast order id, Shopify checkout id, Square payment id). When set on create via `POST /transactions` or `POST /marketplace/accrue`, the unique `(orgId, externalTransactionId)` index makes the call permanently idempotent — a redelivered upstream webhook returns the existing row at HTTP 200 instead of double-crediting. reverses_transaction_id: type: string nullable: true description: | Set on a compensating row created by `/marketplace/reverse`. Points at the original transaction this row reverses. The original is reversed at most once (enforced by a unique constraint). reason_text: type: string nullable: true description: | Operator-visible reason for a reversal ("Customer refunded the order"). Persisted on the COMPENSATING row, not the original. test_mode: type: boolean description: | True when posted via a `pk_test_…` key. Test rows still write to the ledger and still fire webhooks (so partner sandbox integrations can verify their receivers), but DO NOT update Customer / Card / Enrollment aggregates and are excluded from operator dashboard rollups. created_at: type: string format: date-time Error: type: object properties: error: type: object required: - type - message - code properties: type: type: string enum: - authentication_error - permission_error - rate_limit_error - validation_error - not_found - idempotency_error - server_error message: type: string code: type: string param: type: string responses: ValidationError: description: Validation failed headers: X-Request-Id: $ref: '#/components/headers/XRequestId' X-API-Version: $ref: '#/components/headers/XAPIVersion' X-RateLimit-Limit: $ref: '#/components/headers/XRateLimitLimit' X-RateLimit-Remaining: $ref: '#/components/headers/XRateLimitRemaining' X-RateLimit-Reset: $ref: '#/components/headers/XRateLimitReset' content: application/json: schema: $ref: '#/components/schemas/Error' Unauthorized: description: Missing / invalid / expired API key headers: X-Request-Id: $ref: '#/components/headers/XRequestId' X-API-Version: $ref: '#/components/headers/XAPIVersion' X-RateLimit-Limit: $ref: '#/components/headers/XRateLimitLimit' X-RateLimit-Remaining: $ref: '#/components/headers/XRateLimitRemaining' X-RateLimit-Reset: $ref: '#/components/headers/XRateLimitReset' content: application/json: schema: $ref: '#/components/schemas/Error' Forbidden: description: API key is missing the required scope headers: X-Request-Id: $ref: '#/components/headers/XRequestId' X-API-Version: $ref: '#/components/headers/XAPIVersion' X-RateLimit-Limit: $ref: '#/components/headers/XRateLimitLimit' X-RateLimit-Remaining: $ref: '#/components/headers/XRateLimitRemaining' X-RateLimit-Reset: $ref: '#/components/headers/XRateLimitReset' content: application/json: schema: $ref: '#/components/schemas/Error' NotFound: description: Resource not found headers: X-Request-Id: $ref: '#/components/headers/XRequestId' X-API-Version: $ref: '#/components/headers/XAPIVersion' X-RateLimit-Limit: $ref: '#/components/headers/XRateLimitLimit' X-RateLimit-Remaining: $ref: '#/components/headers/XRateLimitRemaining' X-RateLimit-Reset: $ref: '#/components/headers/XRateLimitReset' content: application/json: schema: $ref: '#/components/schemas/Error' RateLimited: description: Per-key rate limit exceeded headers: X-Request-Id: $ref: '#/components/headers/XRequestId' X-API-Version: $ref: '#/components/headers/XAPIVersion' X-RateLimit-Limit: $ref: '#/components/headers/XRateLimitLimit' X-RateLimit-Remaining: $ref: '#/components/headers/XRateLimitRemaining' X-RateLimit-Reset: $ref: '#/components/headers/XRateLimitReset' Retry-After: $ref: '#/components/headers/RetryAfter' content: application/json: schema: $ref: '#/components/schemas/Error' headers: XRequestId: description: | Unique id for this request. Echo this in your support tickets and we can trace the exact call in the audit log on the API key detail page. schema: type: string XAPIVersion: description: | Date-versioned schema marker. The current value is `2026-05-04`. Bumps follow the 12-month deprecation policy documented in the in-dashboard docs page. schema: type: string XRateLimitLimit: description: Total requests permitted per minute for this credential. schema: type: integer XRateLimitRemaining: description: Requests left in the current 60s window. schema: type: integer XRateLimitReset: description: Unix-seconds timestamp when the current window refills. schema: type: integer RetryAfter: description: | Seconds to wait before retrying. Only emitted on 429 responses. schema: type: integer securitySchemes: bearerAuth: type: http scheme: bearer bearerFormat: pk_live_… / pk_test_… or perk_at_… ```` ## Related topics - [List transactions](/api-reference/transactions/list-transactions.md) - [Post a transaction (stamp / redeem / adjust)](/api-reference/transactions/post-a-transaction-stamp-redeem-adjust.md) - [Find-or-create customer + post transaction in one call](/api-reference/marketplace/find-or-create-customer-+-post-transaction-in-one-call.md) - [Idempotency and retries](/fundamentals/idempotency.md) - [Go-live checklist](/support/go-live-checklist.md)