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identifiers

Invoice identifiers, UUIDs, IRNs and access keys

Distinguish invoice numbers, authority UUIDs, hashes, access keys, KSeF numbers and network endpoint IDs.

invoice UUIDIRN CUFE access keyelectronic invoice reference

What it means

Invoice numbers identify documents within an issuer sequence, while UUIDs, IRNs, CUFEs, access keys and authorization codes may be generated or confirmed by national systems.

Buyer references, purchase orders and preceding-invoice references serve separate business purposes and must not be mixed.

Implementation method

  1. 1
    Store every identifier with an explicit type and issuer.
  2. 2
    Validate structure or checksum before submission when an algorithm is public.
  3. 3
    Preserve authority-generated values exactly.
  4. 4
    Use document references to link corrections, credit notes and cancellations.

Common mistakes

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Using one database field for every reference

Build an explicit control or test case for this condition.

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Removing leading zeros

Build an explicit control or test case for this condition.

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Recalculating authority-generated hashes

Build an explicit control or test case for this condition.

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Assuming valid syntax confirms active status or ownership

Build an explicit control or test case for this condition.

Questions and answers

Does a valid checksum prove an invoice exists?

No. It only confirms internal consistency of the identifier. Use the authority status service for existence and status.

Should invoice IDs be reused after rejection?

Rules differ. Keep the rejected attempt and follow the authority’s numbering and resubmission requirements.

Can EInvoiceLab officially certify invoice identifiers?

No. EInvoiceLab can inspect, prepare and explain technical data, but official conformance, delivery or acceptance depends on the active authority, network, accredited provider and validation artefacts.

Should I keep the original structured file?

Yes. Preserve the original XML or JSON, its hash, every validation report and the final authority or network response. A readable PDF should not replace the source document.