Relation, authorisation and sequence errorsRelation & missing element

CDS12024Uniqueness Error: The value declared should be unique

HMRC explanation

Uniqueness error
You have declared a value and repeated it, when that is not allowed.
Check the entries for these data elements: 1/11 - additional procedure code can only be used once on each item 1/6 - item number cannot be repeated on the declaration 2/3 -ARC number declared with document code C651 can only be used on one declaration 4/9 - addition or deduction code can only be used once at header level or once with each item 2/3 - licence ID cannot be repeated on the same item

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

What to check across the Relation, authorisation and sequence errors

Two elements, or a value and a rule, disagree. Read both elements together: completing one element with a particular code often requires another value, and the fault is frequently in the element you did not change. The family also covers parties and authorisations that are not recognised, references that must be unique, and messages sent out of sequence.

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