The NHI has enough numbers at the current rates of allocation to assign to people until 2025. The Ministry is working with the sector to introduce a change to the NHI number format to extend the range of NHI numbers available.
This involves checking and (where necessary) upgrading the health sector’s IT systems which record NHI numbers to accept a new format. This work is underway now to allow time for these checks and any upgrades to take place.
NHI numbers will start to be issued in the new format from 1 October 2025.
What are the format changes?
At the moment, NHI numbers are a unique 7-character number in the format AAANNNC (3 alpha, 3 numeric and one numeric check digit). The new format will be AAANNAX (3 alpha, 2 numeric, 1 alpha and one alpha check digit).
The first new format NHI number will be issued from 1 October 2025.
NHI numbers are currently issued sequentially on the first six characters, e.g ZAA0067, ZAA0075, ZAA0083, [...] ZAB0003, ZAB0011, ZAB0020, ZAB0038, and so on.
This will change with the new format NHI numbers. NHI numbers will be issued in sequential order of the first letter, starting with A’s, and then a randomised allocation of the next 5 characters, with the last character an alpha check digit. e.g. ACA31FM, ASE37QK, ARE62RS, […] BGJ06AS, BGA44DT, BWT41BY.
Details of the change can be found in the HISO 10046:2023 Consumer Identity Standard.
What this means for the health and disability sector
Sector systems that use NHI numbers will need to make sure they can use both the current NHI numbering format and the new format which will come into effect 1 October 2025.
Some systems may need to be upgraded, and it’s important that sufficient time is allowed for this work. We recommend that systems are ready to accommodate the new format well ahead of the planned cutover date of 1 October 2025.
Changing to the alpha/numeric/alpha format and retaining the existing 7 character length is considered the option that will have the least impact on the sector, and is unlikely to require a change in most databases.
The costs of upgrading any systems is expected to be managed by software vendors and software providers. The NHI represents a fundamental health system standard.
Frequently Asked Questions
What is the NHI format change?
The NHI numbering system is being changed to include both the current format AAANNNC (3 alpha, 3 numeric and one numeric check digit) and the new format AAANNAC (3 alpha, 2 numeric, 1 alpha and one alpha check digit). Two variants of the check digit algorithm will be implemented to allow for the current NHI number format having a numeric check digit and the new format having an alphabetic check character.
The two formats will co-exist (i.e. ‘old’ format numbers will not be replaced) and the new format will not be issued until the current format has been exhausted.
This approach is detailed in the updated HISO 10046 Consumer Health Identity Standard.
Why do we need to change the NHI format?
We need to change the format because we are running out of NHI numbers to assign using the current format. Approximately 16,000 NHIs are issued each month (~200,000 per annum) and we are planning to cut across to the new format on the 1st of October 2025.
How was the change consulted on before agreeing the new format?
The NHI support team identified a preferred option in 2017 and referred this to the Health Information Standards Organisation (HISO). In 2018 there was a formal public comment process - refer https://www.health.govt.nz/publication/nhi-number-format-change-public-comment-document. The submissions received were overwhelming in favour of the recommended option.
Why was the option selected?
Retaining the existing NHI character length and changing the alpha/numeric character sequence was deemed to be the lowest impact option available.
What is the expected timing of the change to the NHI number format?
The new format will not be issued by the production NHI system until October 2025.
It is recommended that systems which use the NHI are changed to accommodate the new format as soon as possible.
Test NHIs will be made available in the pre-production compliance test environment to facilitate sector testing.
What is happening in respect of national system changes?
The NHI UAT system has been upgraded to support the new format, however the new format will not be issued by the NHI production system until 1 October 2025.
National system changes will be planned and implemented to meet this timeline.
What are the implications of these changes for the sector?
Systems that store the NHI number and/or interact with the NHI system will need to ensure they can accommodate both the old format and the new format. Some systems may also need to implement the new check digit calculation if they currently perform NHI check digit validations.
In addition, because the new format will end with two alpha characters, facilities will need to ensure that these are accommodated when filing physical patient records.
Is the sequencing of changes in the sector important, e.g. what if the sector make changes ahead of national system changes?
It is recommended that systems are changed to accommodate the new format as soon as possible to allow a comfortable lead time before the first numbers are issued in the new format. The sequencing of changes is largely irrelevant, however all systems that use the NHI must be upgraded to accommodate the new format before 1 October 2025.
What testing is required and how will Te Whatu Ora support this?
Te Whatu Ora’s NHI UAT compliance environment supports the new format and test NHI numbers. Compliance tests are available to support sector testing.
Please contact Integration@health.govt.nz for further detail.
Who will pay health IT vendors to accommodate the new format?
Te Whatu Ora will not fund software vendors to implement support for the new NHI format.
It is expected that software vendors will absorb this cost and/or it will be dealt with as a contractual issue between the software user and the software provider on the basis that the NHI represents a fundamental health system standard and that vendors are generally paid maintenance and support fees to cover changes of this nature.
Why has the check digit algorithm for the new format been changed to use mod 23 instead of mod 24?
Implementation and testing of the new check digit algorithm identified a weakness with the algorithm which means it failed to identify an unacceptably high number of character substitutions. In recognition that we have one chance to get this right before the new NHI number format starts to be issued, we have changed the check digit algorithm to use a modulus 23 operator, rather than a modulus 24 operator, retaining the existing sequence of factors (7, 6, 5, 4, 3, 2). This will reduce character substitution detection failures from an unacceptably high rate of 7%, to approximately 0.2%. Importantly, it also resolves an issue where “1” and “7” could be freely substituted in the number section of the NHI.
Not every IT system that stores the NHI validates the check digit, however those that do will need to ensure they are using a modulus 23 operator, rather than a modulus 24 operator, when calculating the check sum. An updated version of the HISO 10046 Consumer Health Identity Standard was published on 20 April 2023 describing this change.
What happens if the NHI system runs out of numbers in the current format, before 1st October 2025?
The NHI system has a number of historical gaps in the existing format range. These gaps have been reserved for NHI pre-allocation and other purposes.
In the event we reach the end of the current format sequence before 1 October 2025, these gaps will be used to bridge any shortfall until we start issuing new format NHI numbers.
Why will NHI Numbers be issued in a random sequence (non-sequential) in the new format?
New format NHI numbers will be issued in order of the first letter, starting with A’s, and then a randomised allocation of the next 5 characters e.g., ACA31FM, ASE37QK, ARE62RS, […] BGJ06AS, BGA44DT, BWT41BY.
The decision to issue numbers this way has been taken to minimise the incidence of identity confusion, particularly when dealing with multiple births.
If you would like to know more about what the NHI number format changes might mean for you, please contact firstname.lastname@example.org