Relation, authorisation and sequence errorsRelation & missing element

CDS12155Uniqueness Error: Only one instance of 999L may be declared in D.E. 2/3 per goods item

HMRC explanation

Uniqueness Error

The document code 999L can only be declared once per goods item. It does not have to be declared for each measure for which a waiver applies on that goods item. For example, if a goods item has two measures for which 999L is available to declare a waiver, declaring it once for that goods item will suffice to satisfy both measures. Declaring it twice will result in this rejection.

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