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Reduce errors when using data from a passport chip

Passports issued by Her Majesty’s Passport Office (HMPO) conform to ICAO 9303, which is the international specification for machine-readable travel documents.

Many of these passports contain a near-field communication (NFC) chip which holds a copy of the document’s data.

Valid passports may fail a Document Checking Service (DCS) check when using data provided by the passport’s chip rather than the information printed on the passport’s photo page.

Understanding why valid passports might return valid: false

The data on the chip and in the printed Machine-Readable Zone (MRZ) uses a smaller set of characters (0-9, A-Z) than the printed information in the Visual Inspection Zone (VIZ).

HMPO validates passports against the VIZ data, not the MRZ data. Some passport holders’ names will appear differently in MRZ and VIZ formats because of the character omission or replacement.

Characters outside the MRZ set are either omitted or replaced with a filler character (<) following these rules:

  • apostrophes () are omitted, for example, O’NEILL (VIZ) and ONEILL (MRZ)
  • spaces are replaced with <, for example, ANNA MARIE (VIZ) and ANNA<MARIE (MRZ)
  • hyphens (-) are replaced with <, for example, ANNA-MARIE (VIZ) and ANNA<MARIE (MRZ)
  • accents and other non-alphanumeric characters (á,ß, Д) should be replaced according to Section 6 of ICAO 9303, for example, ZOË (VIZ) and ZOE (MRZ)

DCS checks using MRZ data from the passport chip will not match the VIZ data used by HMPO and your service will receive a valid: false response.

Example of a failing check on a valid passport

Imagine a holder of a valid passport with a single forename, “Sarah-Jane”.

This is encoded in the MRZ as SARAH<JANE and in the VIZ as SARAH-JANE.

As the filler character can mean a hyphen or a space, the forename field provided by the MRZ has 2 possible interpretations: “SARAH-JANE” and “SARAH JANE”.

Both of these interpretations pass DCS field validation but only one is a valid document. The other will return valid: false.

Without consulting the VIZ data, there is no way to tell which interpretation is correct.

Reduce the number of incorrectly failed checks

You can improve the accuracy of the DCS checks that use data from the passport chip, for example:

  • if the initial check fails, allow the user to input their passport data manually
  • if there are multiple interpretations, submit a DCS check for both (each request will contribute to your quota)
This page was last reviewed on 21 September 2020.