Relation, authorisation and sequence errorsRelation & missing element

CDS12117Relation error: Importer (DE 3/16) & Buyer (DE 3/27) must not be the same party

HMRC explanation

Relation error
You have declared the same EORI for the Importer and Buyer on an import declaration.

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