Versioning

The current REST API version is v3. The base URL reflects the version:

https://api.efiling.co.uk/3/

Version increments

Versions increment in whole numbers. Users are informed prior to release.

• Non-breaking changes do not receive a version increment. Examples: a new value added to a response, a new optional parameter on a request.
• Breaking changes require a version increment. A breaking change is one where the existing request or response shape is no longer compatible, either through removal or through incompatible modification of existing fields.

Deprecation policy

When a new version deprecates an older one, we give between 3 and 12 months’ notice before the deprecated version is withdrawn. The exact window depends on the scope and impact of the change — small surface-area changes land on the shorter end, broader changes on the longer end. During the notice window the older version continues to function alongside the new version so integrators can migrate on their own schedule.

Exception: legal or regulatory changes mandated by Companies House may require a shorter notice period. Where that happens we communicate the constraint and the accelerated timeline as early as possible.