Free tool · HMRC error codes

CDS error code decoder

Paste the error from a rejected declaration, a list of codes or a single code. The decoder picks out every CDS error code and shows HMRC's description, the class of error and what to check before you resubmit.

  • 181 HMRC codes
  • List of 9 June 2026
  • Runs in your browser
  • Free, no sign-up

Any case, with or without a space or hyphen (cds 12158, CDS-12158). Results appear as you type; nothing you paste leaves this page.

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How it works

From a rejection message to what to check

  1. 01

    Finds every code

    A CDS rejection names each error by a code: CDS followed by five digits. The decoder reads any case, with or without a space or hyphen, ignores the rest of the text and lists each code once, in the order it first appears.

  2. 02

    Shows what HMRC says

    Each code is matched against the 181 codes in HMRC's published list of 9 June 2026. You see HMRC's description, unchanged, and the class of error it names: obligation, relation and missing element, domain and value, authorisation or external validation.

  3. 03

    Says what to check

    Guidance on what to look at before you resubmit: for the code itself where we have written it, otherwise for its series. HMRC's full explanation of every code is one click away.

A code the decoder does not recognise is either mistyped or newer than HMRC's list of 9 June 2026. Browse all 181 CDS error codes by series.

A declaration that clears CDS can still be wrong

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Source: HMRC, Customs Declaration Service error codes, Open Government Licence v3.0. GOV.UK publication · Licence