Stream real-time PSC filing events from Companies House using the Streaming API
domain: developer-specs.company-information.service.gov.uk · 6 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
Obtain a separate streaming API key (distinct from the Public Data API key) from the Companies House Developer Hub
Open a long-lived HTTP GET to https://stream.companieshouse.gov.uk/persons-with-significant-control with Authorization: Basic YOUR_STREAMING_KEY_BASE64; the connection streams newline-delimited JSON events
To resume after a disconnect, reconnect with ?timepoint={last_received_timepoint} query parameter where timepoint is the numeric value from the last event's resource.timepoint field
Parse each event for event.type ('changed', 'deleted'), event.data.company_number, and event.data.natures_of_control changes
Implement a back-off strategy: on HTTP 429 response wait at least 60 seconds before reconnecting to avoid IP-level blocking
Cap concurrent streaming connections at 2 per API key; additional connection attempts cause the oldest connection to be closed by the server
Known gotchas
The streaming API key and the REST API key are different credentials issued separately; using a REST key on the streaming endpoint returns 401
Event data in the stream may arrive out of order relative to filing timestamps; use the timepoint value for ordering, not the event timestamp
The streaming API does not guarantee delivery of every micro-event; for compliance-critical use cases, supplement with scheduled polling of the REST PSC endpoint
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