generated: '2026-08-12'
method: searched
source: https://open-docs.flashexpress.com/#response-code
note: >-
  Flash Express publishes a complete response-code registry in the Constants section of the
  FlashExpress Open API reference. Every code below is transcribed verbatim from that table;
  the `remediation` field is API Evangelist's reading of the published meaning and the
  documented Q&A, and is marked as such. This is an envelope-code catalog, not RFC 9457
  problem details — codes travel in the `code` field of the JSON body and the HTTP status
  line is not the error channel.
format: envelope
rfc9457: false
envelope:
  code: integer
  message: string
  data: object
  success_value: 1
  http_status_carries_error: false
  note: >-
    A business error is returned with a normal HTTP 200 and a non-1 `code`. Callers must
    branch on `code`, never on HTTP status alone.
classes:
- range: '1'
  meaning: success
- range: '0'
  meaning: internal server error
- range: 1000+
  meaning: specific business errors
problems:
- code: 1
  title: success
  class: success
- code: 0
  title: internal server error
  class: server
  remediation: Retry with backoff. Note there is no idempotency key, so retrying a create may collide with code 1003.
  remediation_source: api-evangelist-derived
- code: 1000
  title: Failed to submit
  class: request
  remediation: >-
    Published Q&A: "There are errors in the request body, please check again the symbols in
    the request body, together with the request url." Most often a malformed or
    incorrectly urlencoded body, or the wrong request URL.
  remediation_source: https://open-docs.flashexpress.com/#basic-information
- code: 1001
  title: customer not found
  class: identity
  remediation: Verify mchId is the merchant number issued by Flash Express and matches the environment being called.
  remediation_source: api-evangelist-derived
- code: 1002
  title: invalid signature
  class: authentication
  remediation: >-
    Published Q&A: recompute the signature by sorting non-empty parameters by ASCII code of
    the parameter name ascending, joining as key=value pairs, appending &key=<secret>, taking
    SHA256 and uppercasing. Exclude the sign parameter and any whitespace-only value; sign
    before urlencoding; parameter names are case sensitive.
  remediation_source: https://open-docs.flashexpress.com/#basic-information
- code: 1003
  title: Order is exists
  class: conflict
  remediation: >-
    The outTradeNo (or merchant tracking number) has already been used for this merchant.
    This is duplicate rejection, not idempotent replay — the original order payload is not
    returned. Look the order up by the existing reference rather than re-creating it.
  remediation_source: api-evangelist-derived
- code: 1004
  title: Sender address does not match
  class: validation
  remediation: Sender province/city/district names must match the Flash standard location tree returned by the address_core operation.
  remediation_source: api-evangelist-derived
- code: 1005
  title: Destination address does not match
  class: validation
  remediation: Destination province/city/district names must match the Flash standard location tree returned by the address_core operation.
  remediation_source: api-evangelist-derived
- code: 1006
  title: order not found
  class: not-found
- code: 1007
  title: warehouse not found
  class: not-found
  remediation: Call POST /open/v1/warehouses to list valid warehouseNo values for this merchant.
  remediation_source: api-evangelist-derived
- code: 1008
  title: COD Service is not registered
  class: entitlement
  remediation: Cash-on-delivery must be enabled on the merchant account by Flash Express before codEnabled can be used.
  remediation_source: api-evangelist-derived
- code: 1009
  title: COD amount cannot be negative value
  class: validation
  remediation: codAmount is an integer in cents (1 THB = 100 cent) and must be zero or positive.
  remediation_source: api-evangelist-derived
- code: 1010
  title: Imcomplete schedule of pickup is exists, no schedule of pickup is required
  class: conflict
  remediation: An open courier pickup notification already exists. Query notifications before scheduling another.
  remediation_source: api-evangelist-derived
  note: Title transcribed verbatim from the published table, including the "Imcomplete" spelling.
- code: 1011
  title: This courier notification can't be cancelled
  class: state
- code: 1015
  title: Parcel is picked up, not allowed to cancel
  class: state
  remediation: Cancellation is only valid before pickup. After pickup the parcel must be handled through the returns/withdrawal flow.
  remediation_source: api-evangelist-derived
- code: 1018
  title: Either sender's address and warehouse no should be sent
  class: validation
  remediation: Supply either an explicit sender address block or a warehouseNo, not neither.
  remediation_source: api-evangelist-derived
- code: 1019
  title: pno and mchId not match
  class: authorization
  remediation: The tracking number belongs to a different merchant account. Parcels are scoped to the owning mchId.
  remediation_source: api-evangelist-derived
- code: 1020
  title: insureDeclareValue cannot be negative value
  class: validation
  remediation: insureDeclareValue is an integer in cents and must be zero or positive.
  remediation_source: api-evangelist-derived
- code: 1021
  title: Postal Code should be 5 digit number
  class: validation
- code: 1022
  title: Sender's address are not in service range yet
  class: coverage
  remediation: The pickup address falls outside the current Flash Express service area.
  remediation_source: api-evangelist-derived
summary:
  problem_count: 22
  business_error_count: 20
  classes: [success, server, request, identity, authentication, conflict, validation, not-found, entitlement, state, authorization, coverage]