Version Control

Overview

The NZ Banking Data API Specification was designed to create an API based payments ecosystem for NZ and simplify partnering in the payments industry. These standards enable Banks to develop API endpoints to an agreed standard so that Third Parties can build web and mobile applications that make it easier for banking customers to pay for goods and services. This main specification provides a description of the elements that are common across all the NZ Banking Data APIs.

This specification should be read in conjunction with the individual NZ Banking API Specifications for:

• Account Information API Specification

• Payment Initiation API Specification

• Event Notification API Specification

The PNZ API standards are based on the UK Open Banking standard. The PNZ API standards include adjustments to and place limitations on the UK Open Banking standard to make the standards more suitable to the NZ market. The Open Banking standard is now in the public domain; the PNZ API standards are not in the public domain as they are currently under development. Access to the PNZ API standards is currently limited to those organisations approved/authorised to operate in the NZ payments API ecosystem - Bank's and Third Parties. Approval and authorisation is managed by Payments NZ.

Overview Diagram

The figure below provides a general outline of a flow using the NZ Banking Data APIs.

Open

Steps

Step 1: Agree Consent

• This flow begins with a Customer consenting to allow a Third Party to access the Customer's protected resources with the API Provider.

Step 2: Create Consent

• The Third Party connects to the API Provider that services the Customer's account(s) and creates a consent.

• The API Provider responds with an identifier for the consent (the ConsentId).

Step 3: Authorise Consent

• The Third Party initiates the authorisation flow for the Customer to authorise the consent.

• The Customer authorises the consent with the API Provider. The Customer will only be able to authorise or reject the consent details in its entirety.

Step 4: Access Protected Resources

• The API Provider authenticates the Third Party and Customer has authorised consent for the request before providing access to protected resources.

Step 5: Retrieve Consent Status

• The Third Party may retrieve the status of the consent (with the ConsentId).

Document Structure

This document consists of the following parts:

• Overview: Provides an overview of the Payments NZ API Standards and the key decisions and principles that contributed to the specification.

• Basics: The section begins with an introduction to how the APIs are used.

• Security & Access Control: Specifies the means for Third Parties and Customers to authenticate themselves and provide consent.

• Data Model: Describes the data model for the API payloads.

Known Issues

This document and its sub-pages must be read in conjunction with the Specification Issues Log - v3.0.

Design Principles

RESTful APIs

The API adheres to RESTful API concepts where possible and sensible to do so.

However, the priority is to have an API that is simple to understand and easy to use. In instances where following RESTful principles would be convoluted and complex, the principles have not been followed.

References:

• The highest level Data Description Language used is the JSON Schema : http://json-schema.org/

• Best Practice has also been taken from the Data Description Language for APIs; JSON API : http://jsonapi.org/

• The Interface Description Language used is the Openapi Specification version 3.0 (historically referred to as Swagger): http://swagger.io/

Standards

The PNZ API Working Group principles for developing API standards:

• PNZ API Working Group will adopt existing standards where relevant/appropriate to minimise re-inventing the wheel.

• PNZ API Working Group will work with other relevant bodies to align with, contribute to and/or adopt other Standards work, especially relating to Open Banking UK.

Extensibility

It is intended that the API flows will be extended to cater for more complex use-cases in subsequent releases, and we have kept this in mind during the design.

When extensibility by API providers is allowed, this is explicitly stated in the specifications, and is required to be documented by API providers on their developer portal.

Idempotency

Idempotency is difficult to implement consistently and leverage consistently. 

As a result, idempotency is used sparingly in these specifications; with a preference to allow Third Parties to simply re-submit a request under failure conditions.

APIs have been defined to be idempotent, where not doing so would cause a poor Customer user-experience or increase false positive risk indicators.

Message Signing

Message signing must not be implemented for the Account Information API and Payment Initiation API request and responses.

Message Encryption

Message encryption must not be implemented for the Account Information API and Payment Initiation API request and responses.

Agnostic to Payment Schemes

The API will be designed so that it is agnostic to the underlying payment scheme that is responsible for carrying out the payment.

Status Codes

API responses use two status codes that serve two different purposes:

• The HTTP Status Code reflects the outcome of the API call (the HTTP operation on the resource). Granular Functional Error Codes are specified as part of API Error Response Structure.

• The Status field in a resource payload reflects the status of the resource.

Communicating a rejection status is done in two ways:

• If the API Provider establishes a rejection scenario with payload or any contextual error during the API call, the API Provider must reject the request immediately with the appropriate 4xx code.

• If the API Provider establishes a rejection scenario with the consent after the API call, the API Provider must set the Status of the consent to Rejected.

Unique Identifiers (Id Fields)

A REST resource should have a unique identifier (e.g. a primary key) that may be used to identify specific instances of a resource. These unique identifiers are used to construct URLs to identify and address specific instances of a resource.

However, considering that some of the resources described in this specification do not have a primary key in the system of record, the Id fields will be optional for some resources.

An API Provider must ensure that populated Id fields values are unique and immutable.

Categorisation of Implementation Requirements

The functionality, endpoints and fields within each resource are categorised as 'Mandatory' or 'Optional'.

API Providers must make documentation available to Third Parties (e.g. on their developer portals) specifying which 'Optional' endpoints and fields are implemented for any given implementation of the specification.

Mandatory

For functionalities and endpoints: 

• An API Provider must implement an endpoint that is marked Mandatory.

• An API Provider must implement functionality that is marked Mandatory.

For fields:

• A Third Party must specify the value of a Mandatory field.

• An API Provider must process a Mandatory field when provided by the Third Party in an API request.

• An API Provider must include meaningful values for Mandatory fields in an API response.

Optional

For functionalities and endpoints:

• An API Provider may implement an Optional endpoint.

• An API Provider may implement Optional functionality.

For fields:

• A Third Party may specify the value of an Optional field.

• An API Provider must process an Optional field when provided by the Third Party in an API request. If the API Provider cannot support a particular value in an Optional field, the API Provider must reject the request and respond with an error.

• An API Provider may specify the value of an Optional field in an API response.

Open Banking UK

The principles we have applied to re-use of the Open Banking UK specifications are:

• Only resources that are required will be included in the API specification.

• We will modify Open Banking UK elements where the existing standard does not cater for the NZ Market (such as adding the "BECSElectronicCredit" Scheme). 

Basics

Actors

In the NZ context, there are three main actors (API Provider, Third Party, and Customer).

The upstream Open Banking UK standard uses PSD2 parlance and acronyms that are not applicable or relevant to the New Zealand market. Below is a summary of the NZ equivalent for many common PSD2 terms.

Character Encoding

The API requests and responses must use a UTF-8 character encoding. This is the default character encoding for JSON (RFC 7158 - Section 8.1).

However, an API Provider's downstream system may not accept some UTF-8 characters, such as emoji characters (e.g. "Happy Birthday 🎂🎂!" may not be an acceptable Payment Reference). If the API Provider rejects the message with a UTF-8 character that cannot be processed, the API Provider must respond with an HTTP 400 (Bad Request) status code.

Date Formats

An API Provider must accept all valid ISO-8601 date formats including its permitted variations (e.g. variations in how the timezone is defined, dates with or with a seconds or milliseconds part etc.) in the requests.

All dates in the JSON payloads are represented in ISO 8601 date-time format. All date-time fields in responses must include the timezone. For Example:

All dates in the query string (e.g., filter parameters) are represented in ISO 8601 date-time format and must not include the timezone.

If the DateTime contains a timezone, the API Provider must ignore the timezone component. The filter values will be assumed to refer to the same timezone as the timezone in which the resource is maintained.

For example:

All dates in the HTTP headers are represented as RFC 7231 Full Dates. An example is below:

All dates in the JWT claims are expressed as a JSON number, representing the number of seconds from 1970-01-01T0:0:0Z as measured in UTC until the date/time. 

Resource URI Path Structure

The path of the URI must follow the structure below (from the OB API Release Management document).

• [participant-path-prefix]/open-banking-nz/[version]/[resource]/[resource-id]/[sub-resource]

This consists of the following elements:

• [participant-path-prefix]
  An optional API Provider specific path prefix.

• open-banking-nz
  The constant string "open-banking-nz".

• [version]
  The version of the APIs expressed as /v[major-version].[minor-version]/.

• [resource]/[resource-id]
  Details the resource.

• [sub-resource]
  Details the sub-resource.

An API Provider must use the same [participant-path-prefix] and host name for all its NZ Banking Data API resources.

Examples:

For brevity, the APIs are referred to by their resource names in these documents and in all examples.

Headers

Request Headers

The following headers should be inserted by the Third Party in each API call:

Whether the Customer is present or not-present is identified via the x-fapi-customer-ip-address header. If the Customer IP address is supplied, it is inferred that the Customer is present during the interaction.

The implications to this are:

• API Providers will need to rely on the Third Party's assertion.

Response Headers

HTTP Status Codes

The following are the HTTP response codes for the different HTTP methods - across all API endpoints.

An API Provider may return other standard HTTP status codes (e.g. from gateways and other edge devices) as described in RFC 7231 - Section 6.

An API Provider must respond with error response in the OAuth/OIDC flow with mandatory alignment of error codes to those specified in OpenID Connect Core Specification Section 3.1.2.6.

An API Provider must respond with the NZ Banking Data Error Response Structure for all errors during API Calls.

403 (Forbidden) v/s 404 (Not Found) v/s 501 (Not Implemented)

When a Third Party tries to request a resource URL with a resource Id that does not exist, the API Provider must respond with a 403 (Forbidden) rather than a 404 (Not Found). This is so API Providers do not accidentally disclose the existence of a resource instance.

E.g., if a Third Party tries to GET /domestic-payments/22289 where 22289 is not a valid DomesticPaymentId, the API Provider must respond with a 403 (Forbidden).

If a Third Party tries to request a resource URL that results in no business data being returned (e.g. a request to retrieve standing order on an account that does not have standing orders), the API Provider must respond with a 200 (OK) and set the array to be empty.

If an API Provider has not implemented an optional API, the API Provider must respond with a 501 (Not Implemented) for requests to that URL.

The table below illustrates some examples of expected behaviour:

403 (Forbidden)

When a Third Party tries to access a resource that it does not have permission to access, the API Provider must return a 403 (Forbidden).

The situation could arise when:

• The Third Party uses an access token that does not have the appropriate scope to access the requested resource.

• The Third Party attempted to access a resource with an Id that it does not have access to. E.g., an attempt to access GET /domestic-payments/1001 where a domestic-payments resource with Id 1001 belongs to another Third Party.

• The Third Party tries to access an account information resource, and the Third Party does not have a consent authorisation with the right Permissions to access the requested resource. E.g., an attempt to access GET /standing-orders when the ReadStandingOrdersBasic permission was not included in the consent authorisation.

• The Third Party tries to access an account/transaction resource and the Third Party does not have a consent authorisation for the AccountId. E.g., an attempt to access GET /accounts/2001 or GET /accounts/2001/transactions when the Customer has not selected AccountId 2001 for authorisation.

• The Third Party tries to access a protected payment resource, and the Third Party does not have a consent authorisation with the right consent parameters to access the requested resource. E.g., an attempt to POST /domestic-payments with a mis-match with the Consent object in the domestic-payment-consent.

When the Third Party uses an access token that is no longer valid, the situation could potentially be remedied by asking the Customer to re-authenticate. This should be indicated by a 401 (Unauthorized) status code.

401 (Unauthorized)

When the Third Party uses an expired access token, the API Provider must return a 401 (Unauthorized).

The situation could arise when an API Provider has chosen to expire an access token, reasons may include:

1. The consent has expired (e.g., the expiration date time has lapsed)

2. Suspicious usage of the access token or suspected fraud

3. The Customer has revoked consent

This error can potentially be remedied by asking the Customer to re-authenticate or authenticate with the right permissions.

429 (Too Many Requests)

When a Third Party tries to access a resource too frequently the API Provider may return a 429 (Too Many Requests). This is a non functional requirement and is down to individual API Providers to decide throttling limits.

This situation could arise when:

• A Third Party decides to implement "Real Time Payment Status" functionality for its users and implements this badly by polling a GET endpoint or an Idempotent POST endpoint in excess of the API Provider's fair usage policy to provide pseudo "real-time" Status updates to the user.

• A Third Party decides to use the Single Immediate Payment endpoint as if it were a batch payment facility and sends a large number of payment requests in a very short space of time such that it exceeds the API Provider's fair usage policy. 

Pre-Conditions

The following pre-conditions must be satisfied in order to use these APIs:

Pre-conditions for Third Parties

1. The Third Party must have completed onboarding with PNZ.

2. The Third Party must have completed registration with each of the API Providers that it wants to transact with and have been issued with a client-id with required scopes.

3. The Third Party must have valid network and signing certificates issued by one of the accepted Certificate Authorities.

Pre-conditions for API Providers

1. The API Provider must have completed onboarding with PNZ.

2. The API Provider must have valid network and signing certificates issued by one of the accepted Certificate Authorities.

Idempotency

An idempotency key is used to guard against the creation of duplicate resources when using the POST API endpoints (where indicated). 

If an idempotency key is required for an API endpoint:

• The x-idempotency-key provided in the header must be at most 40 characters in size. If a larger x-idempotency-key length is provided, the API Provider must reject the request with a status code is 400 (Bad Request).

• The API Provider must treat a request as idempotent if it had received the first request with the same x-idempotency-key from the same Third Party in the preceding 24 hours.

• The API Provider must not create a new resource or modify an existing resource for a POST request if it is determined to be an idempotent request. 

• The Third Party must not change any part of an API request (i.e., parameters, header or body) while using the same x-idempotency-key. The API Provider may treat this as a fraudulent action.

• If a Third Party attempts a different API request (the parameters, header or body changed) with an x-idempotency-key used in the preceding 24 hours - the behaviour is unspecified - as the result will depend on whether the original request has been successfully received by the API Provider.

• The API Provider must respond to a successful API request with the current resource status (or a status which is at least as current as what's available on existing online channels) and a HTTP status code of 201 (Created).

• The Third Party must not use the idempotent behaviour to poll the status of resources.

If an idempotency key is not required for an API endpoint:

• The API Provider must ignore the idempotency key if provided.

Filtering

An API Provider must provide limited support of filtering on GET operations that return multiple records.

The filter parameters, are always specific to particular field(s) of the resource, and follow the rules/formats defined under the resource's data dictionary. The format for dates in the filter parameters are defined in the Date Formats section.

Pagination

An API Provider may provide a paginated response for GET operations that return multiple records.

In a paginated response, the API Provider must provide:

• A link to the next page of resources in the Links.Next field of the response if a subsequent page of resource records exists. The absence of a next link would indicate that the current page is the last page of results.

• A link to the previous page of resources in the Links.Prev field of the response if a previous page of resource records exists. The absence of a prev link would indicate that the current page is the first page of results.

• A link to the first page of results in the Links.First field.

• A link to the last page of results in the Links.Last field.

• A "Self" link to the resource in the Links.Self field as with all other API responses, as described in the Links sections.

In a paginated response, the API Provider should ensure that the number of records on a page are within reasonable limits - a minimum of 25 records (except on the last page where there are no further records) and a maximum of 1000 records.

In a paginated response, the API Provider may provide:

• The total number of pages in the Meta.TotalPages field.

This standard does not specify how the pagination parameters are passed by the API Provider and each API Provider may employ their own mechanisms to paginate the response.

If the original request from the Third Party included filter parameters, the paginated response must return only results that match the filter.

API Providers are not expected to implement pagination with transaction isolation. The underlying data-set may change between two subsequent requests. This may result in situations where the same transaction is returned on more than one page.

Archiving

Archiving of consent resources (identified with a ConsentId) will be for API Providers to define based on their internal Legal and Regulatory requirements. Archiving in this context means the ConsentId is no longer available via the API (e.g., a 403 response from a GET /domestic-payment-consents/{ConsentId}).

An API Provider may only archive a consent in these two scenarios:

• The consent is not in the Authorised state - the API Provider may archive the consent 24 hours after the last consent status update (the StatusUpdateDateTime).

• The consent has expired - the API Provider may archive the consent 24 hours after the consent expiration date time.

The implications of this are:

• API Providers must not archive a ConsentId within the first 24 hours of the consent creation

• API Providers may archive a ConsentId that is not in the Authorised state 24 hours after the last state change

• API Providers may archive a ConsentId that is in the Authorised state 24 hours after the consent expiration date (e.g., the ExpirationDateTime for an account-access-consent)

Security & Access Control

Security and access control information is contained in the https://paymentsnz.atlassian.net/wiki/spaces/PaymentsDirectionAPIStandardsDevelopment/pages/1643873861

Data Model

Common Payload Structure

This section gives an overview of the top level structure for the API payloads for the NZ Banking APIs.

The data contained within the Data section is documented with each individual API endpoint.

Request Structure

The top level request structure for the NZ Banking APIs:

Request

Data

The Data section contains the request data for the specific API request.

The structure of this element differs for each API endpoint, and is documented on each API resource sub-page.

Risk

The Risk section contains risk indicators for the specific API request as provided by the Third Party.

The risk indicators contained in this element may be different for each API endpoint. The structure of the Risk section is documented in the section for NZRisk1.

Response Structure

The top level response structure for the NZ Banking APIs:

Response

In line with the principle of RESTful APIs, the full resource must be replayed as part of the response.

Two additional top level sections are included in the response for:

• Links

• Meta

Links

The Links section is mandatory and will always contain absolute URIs to related resources.

An API Provider must provide the "Self" member in an API response. 

If an API provides a paginated response, the Links section must also contain the members "First", "Prev", "Next" and "Last".

Example Links (Self only)

For example:

Example Links

Meta

The Meta section is mandatory, but can be empty. An optional member is "TotalPages" which is specified as an integer (int32) and shows how many pages of results (for pagination) are available.

For example:

Example Meta

Error Response Structure

The error response structure is used to structure the response body for API Provider error responses.

Response

UML Diagram

Open

Data Dictionary

Enumerations

Optional Fields

In objects where the value for an optional field is not specified, the field must be excluded from the JSON payload (i.e., the field must not included in the payload with the field set to null).

In objects where an array field is defined as having 0..n values, the array field must be included in the payload with an empty array.

In the case of empty objects, unless specified, the object must be excluded from the JSON payload.

Enumerations

The specifications include various enumerated data types, where values are fixed to a defined set of alternatives (i.e. static enumerations). These static enumerations are listed on each API Specification page.

Common Classes

This section describes object classes that are reused within the NZ Banking APIs.

NZRisk1

This section describes the NZRisk1 class.

UML Diagram

Notes

• Payments for EcommerceGoods and EcommerceServices should have a MerchantCategoryCode and MerchantCustomerIdentification populated.

• Ecommerce payments which have a delivery address must have the DeliveryAddress populated. The AddressType for the DeliveryAddress object must be set to "DeliveryTo".

• While some of the fields are specific to the Payment APIs, the working group decided to re-use this object for the Account and Transaction APIs as the fields are all optional.

Data Dictionary

Usage Examples

The usage examples for the individual APIs are documented in their respective pages.

This section provides usage examples for some repeating patterns that are used by multiple resources.

Pagination Flows

The example below illustrates how an API Provider may return a paginated response.

The example below illustrates how an API Provider may use the Links section of the payload to navigate to the Next page of the results. 

Error Flows

This section provides some examples of error scenarios and the expected outputs.

Missing or Expired Access Token

This flow assumes that the following Steps have been completed successfully:

• Step 1: Agree Account Access Consent

• Step 2: Create Account Access Consent

• Step 3: Authorise Consent

The Third Party attempts to provide an expired or missing access token to the API Provider in an attempt to Request Data

Incomplete or Malformed Request Payload

This flow assumes that the following Steps have been completed successfully:

• Step 1: Agree Account Access Consent

• Step 2: Create Account Access Consent

• Step 3: Authorise Consent

The Third Party provides a malformed request to the API Provider in an attempt to setup an Account Access Consent.

Missing or Invalid Access Token Scope

This flow assumes that the following Steps have been completed successfully:

• Step 1: Agree Account Access Consent

• Step 2: Create Account Access Consent

• Step 3: Authorise Consent

The Third Party provides a (valid) access token which does not have a valid scope (or link to the correct Permissions) to Request Data

Sudden Burst of API Requests

This flow assumes that the following Steps have been completed successfully:

• Step 1: Agree Account Access Consent

• Step 2: Create Account Access Consent

• Step 3: Authorise Consent

The Third Party provides a (valid) access token which is used to generate a burst of multiple requests to retrieve an accounts resource.

The API Provider can optionally choose to return a 429 Response

Failed Authorisation Consent

This flow assumes that the following Steps have been completed successfully:

• Step 1: Agree Account Access Consent

• Step 2: Create Account Access Consent

The Step 3: Authorise Consent Flow fails to succeed due to the Customer providing invalid credentials to the API Provider, resulting in no Authorization Code being generated.