---
updatedAt: 2026-04-20T19:23:49.000Z
agentTools:
  projectIndex: https://devdocs.helcim.com/llms.txt
---

# Cancel a pending ACH transaction.

# OpenAPI definition

```json
{
  "openapi": "3.0.0",
  "info": {
    "description": "This API covers publicly accessible merchant actions",
    "version": "2.2.0",
    "title": "The Helcim API"
  },
  "servers": [
    {
      "url": "https://api.helcim.com/v2"
    },
    {
      "url": "https://api.helcim.test/v2"
    }
  ],
  "paths": {
    "/ach/transactions/{transactionId}/cancel": {
      "patch": {
        "tags": [
          "ACH Payment"
        ],
        "summary": "Cancel a pending ACH transaction.",
        "operationId": "ach-cancel",
        "parameters": [
          {
            "in": "header",
            "name": "idempotency-key",
            "description": "A UUID-formatted idempotency key. Accepted format is 25-36 alphanumeric characters (including '-' and '_').",
            "required": true,
            "schema": {
              "type": "string",
              "format": "uuid"
            }
          },
          {
            "in": "path",
            "name": "transactionId",
            "description": "The ID of the ACH transaction to cancel.",
            "required": true,
            "schema": {
              "type": "integer"
            }
          }
        ],
        "responses": {
          "200": {
            "description": "The pending ACH transaction was successfully cancelled.",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/Res-7"
                }
              }
            }
          },
          "400": {
            "description": "Invalid request. Likely due to the ACH transaction not being pending.",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/Message"
                }
              }
            }
          },
          "403": {
            "description": "User does not have valid permissions."
          },
          "500": {
            "description": "Unexpected internal error."
          }
        },
        "security": [
          {
            "ApiAccessAuth": []
          }
        ]
      }
    }
  },
  "components": {
    "securitySchemes": {
      "ApiAccessAuth": {
        "description": "API Token with required permissions",
        "type": "apiKey",
        "in": "header",
        "name": "api-token"
      }
    },
    "schemas": {
      "Message": {
        "title": "Generic Response Payload Message",
        "type": "object",
        "properties": {
          "message": {
            "type": "string"
          }
        }
      },
      "Res-7": {
        "title": "ACH Cancel Response Payload",
        "type": "object",
        "properties": {
          "message": {
            "type": "string"
          }
        },
        "example": {
          "message": "Successfully cancelled ACH transaction #34232."
        }
      }
    }
  }
}
```